Which was one of the three cities of refuge Moses set aside east of the Jordan?

Answer: Bezer

Moses set aside Bezer for Reuben, Ramoth in Gilead for Gad, and Golan in Bashan for Manasseh.

“Bezer in the wilderness on the plateau belonging to the Reubenites, Ramoth in Gilead belonging to the Gadites, or Golan in Bashan belonging to the Manassites.”— Deuteronomy 4:43 (BSB)