From the crowd who gathered around Peter and the other apostles, only those who were persuaded by Peter that Jesus is the Christ presented themselves (and we can assume their families, see Acts 16:15, Acts 16:33) for baptism.1 As we have seen already (Acts 2:13), there were some Jews who thought the apostles were drunk and not worth listening to. Presumably they were those who did not respond in obedience to Peter’s word.
41 So those who received his word were baptized, and there were added that day about three thousand souls.