Mark 16:14-16:
4 Later Jesus appeared to the Eleven as they were eating; he rebuked them for their lack of faith and their stubborn refusal to believe those who had seen him after he had risen.
15 He said to them, “Go into all the world and preach the gospel to all creation. 16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.
Jesus did command baptism for salvation and Peter in his speech recorded in Acts also commands the people to confess and be baptized to be saved.
I Peter 3:20-22 also points this out...
In it only a few people, eight in all, were saved through water, 21 and this water symbolizes baptism that now saves you also—not the removal of dirt from the body but the pledge of a clear conscience toward God. It saves you by the resurrection of Jesus Christ, 22 who has gone into heaven and is at God’s right hand—with angels, authorities and powers in submission to him.
Paul saw and was taught by Christ and he was baptized so why doubt the rest of the disciples of having been baptized...it is a command of God...the Great Commission.
Acts 9:19-17:
Then Ananias went to the house and entered it. Placing his hands on Saul, he said, “Brother Saul, the Lord—Jesus, who appeared to you on the road as you were coming here—has sent me so that you may see again and be filled with the Holy Spirit.” 18 Immediately, something like scales fell from Saul’s eyes, and he could see again. He got up and was baptized, 19 and after taking some food, he regained his strength.