Where were the patriarchs buried ? How many burial places did Abraham buy? Is there any contradiction involved ? There are three relevant Bible passages that give us some information that can help us come to a fair conclusion and resolution of issues:
The first reference is regarding the burial place of Jacob as recorded in
"Thus his sons did for him as he had commanded them, for his sons carried him to the land of Canaan and buried him in the cave of the field at Machpelah, to the east of Mamre, which Abraham bought with the field from Ephron the Hittite to possess as a burying place."(ESV)
The second passage is also about Jacob's burial place from the speech of Stephen in Acts 7:15,16:
And Jacob went down into Egypt, and he died, he and our fathers, and they were carried back to Shechem and laid in the tomb that Abraham had bought for a sum of silver from the sons of Hamor in Shechem.(ESV)
The third relevant verse is regarding the burial place of Joseph as recorded in Joshua 24:32:
"As for the bones of Joseph, which the people of Israel brought up from Egypt, they buried them at Shechem, in the piece of land that Jacob bought from the sons of Hamor the father of Shechem for a hundred pieces of money. It became an inheritance of the descendants of Joseph."(ESV)
A little background information could be useful here. Jewish law, though it said little about burial, forbade shifting of burial places. But in Bible times, burial places outside a town or city were shifted as the town or city expanded, to be always located outside the town or city limits.(Prophets and kings were however buried within the city.) Further, dead bodies could be shifted from original grave to graves of parents or close relatives. Also, collecting of bones and putting them away in ossuaries was common then. So shifting of burial places were not taboo or strictly prohibited in those times. In fact one could argue that it is more out of place or uncommon to shift burial places or remove bones nowadays than it was in Bible times.
See this article on Disinterment and this on Death.
Coming back to the issues in question, on the face of it, there is indeed a direct contradiction of facts about the burial place of Jacob as recorded in Gen.50:12,13 ( as being in Machpelah near Hebron) and as spoken by Stephen
(as being in Shechem) in Acts 7:15,16. But this problem is resolved quite easily.
Note that both the Genesis and Acts passages say that it was Abraham that bought both the burial places in Hebron and Shechem respectively (likely at different points in time). The distance between Hebron, close to which place was the cave of Machpelah, and Shechem is over about 140 kilometers. It is absurd to think it was a mixup of places or names between the Genesis and Acts passages. The passages therefore contain deliberately emphasised similarities and differences that needs reconciliation that does not discredit the veracity of both references. Following this principle, one can conclude that Abraham bought not just one but two pieces of land - the cave of Machpelah and the other one at Shechem from the sons of Hamor. Now, where then was Jacob buried ? At Machpelah as the Genesis account says or at Shechem as Stephen says in Acts 7 ? Note, we need to take both the passages as true historical records. Here is a simple attempt at reconciliation. Jacob could indeed have been buried in Machpelah near Hebron first, and then his bones shifted to Shechem (unrecorded in Biblical accounts, but nevertheless plausible, given the prevailing/antecedent practices)and buried there along with his sons (See Acts 7:15,16). In this case, there need be no contradiction and both the Genesis 50:13 and Acts 7:15,16 passages are reconciled.Stephen, in his Acts speech, probably ignored the first burial place of Jacob and only mentioned his subsequent burial place at Shechem, which was probably common knowledge in his time.
There is another conflict of recorded facts in Acts 7:15,16 and Josh. 24:32
(which passage refers to the burial place of Joseph).The Josh.24:32 passage says that Jacob bought a parcel of land from the sons of Hamor which was used to bury Joseph whereas Acts 5:15,16 states that it was Abraham who bought a piece of land from the sons of Hamor wherein Jacob was supposedly buried. The problem here is not the place, Shechem, but rather a question of who bought the plot ( or plots)- Abraham or Jacob. Here is an attempt at reconciliation of both references taking both those passages as true records : Jacob could indeed have bought an additional plot in Shechem from the sons of Hamor ( even adjoining/abutting the one Abraham bought earlier on from the sons of Hamor ) wherein Joseph could have been buried later as recorded in Joshua 24:32. The conflict is thus resolved.
To conclude, there need be no contradiction of facts regarding the burial places of the patriarchs as recorded in Gen. 50:12,13 and Acts 7: 15,16 if one is willing to accept that, unrecorded in the Bible, Jacob's body (or bones) could have been shifted from Machpelah to Shechem.Stephen was probably referring to the final known resting place of Jacob's remains.
There need be no conflict as to the burial plot at Shechem, as recorded in Acts 7:15,16 and Josh.24:32 if one is willing to accept that both Abraham and Jacob bought adjoining plots at Shechem from the sons of Hamor at different points in time respectively to form one big plot ( unrecorded explicitly in the Bible, but nevertheless very plausible), which was the last Biblically recorded resting place of the remains of Jacob, Joseph, his descendents, and his brothers.In fact, this is in perfect agreement with the known practice of burying close relatives ( in this case it was Jacob's remains that was moved closer to his sons.)