Believer's baptism is simply an act showing what the LORD has fulfilled in the Sinners life. That the Sinner died in Christ, was also buried and is now risen as a new creature in Christ.
Romans 6 It is a picture, a symbol. Yet it still is very important, since it is the first command given to a new Christian to fulfil. Why?
Because it requires an act of obedience, because this road of being a Christian is a very hard and even lonely narrow road. You need to lear to say NO to the World and YES to Christ. So the Sinner, at this point after Salvation now a Saint, needs to take a public stand and proclaim that he has laid down the old man and will now serve the Lord Jesus as his King.
THAT IS WHY IT IS SO DIFFICULT for people, especially those who came from infant sprinkling backgrounds, to follow through with this first step of obedience, as it requires a public acknowledgement of yourself and your past being a failure. (By the way, when anyone calls himself a Christian, he is really stating that he himself is a miserable wretch who can only be saved by the almighty hand of God, nothing else. Which happens to be the truth for all of us.)
(It also shows the beautiful place something such as an "altar call" has as it teaches the Sinner to make a public acknowledgement of needing a Saviour from the very first.)
One needs to learn to be obey to the Scriptures, not learn how to wrest or corrupt them. See 2 Pet 3:16 and 2 Cor 2:17 in your KJV Bible.
From Acts 8:36,37 we learn the requirement for someone to be baptised is to first believe with all his heart. So if you can find a baby of a few days/months old who can declare that he believes in the Lord Jesus for salvation, then by all means go ahead and baptise him...