The question of conversion in Christianity as a whole is very different than when you just look at western evangelicals. For someone raised entirely in a christian family and in a church they stay with their entire lives, there may never be a "conversion" since there may never have been a time when they weren't christian.
Most evangelical churches empasize the need in this situation to "make the faith their own", with a subsequent baptism as a teenager or adult. In these churches making a positive decision at some point to become (or remain) a christian is very important.
For many churches that practice infant baptism, there is generally some confirmation process that serves a similar function to adult baptism in evangelical churches. The difference being that one doesn't choose to be a christian, one has to choose not to remain a christian. You're a christian by default, and it requires an act of apostasy to leave.