Many people became believers and joined the other believers.

Acts 2:41-42

41 So the people who believed Peter’s message were baptized. There were about 3,000 [SYN] who joined the group of believers that day. 42 They continually obeyed what the apostles taught, and they very frequently met together with the other believers. And they continually ate together and celebrated the Lord’s Supper, and continually prayed together.