To which city did Barnabas go to look for Saul and bring him back to Antioch?

Answer: Tarsus

Barnabas went to Tarsus to look for Saul, found him and brought him to Antioch, where they taught for a full year.

“Then Barnabas went to Tarsus to look for Saul, and when he found him, he brought him back to Antioch. So for a full year they met together with the church and taught large numbers of people. The disciples were first called Christians at Antioch.”— Acts 11:25-26 (BSB)