During which Persian king's reign did Ezra the scribe travel from Babylon to Jerusalem?

Answer: Artaxerxes

Ezra went up to Jerusalem in the seventh year of King Artaxerxes, who granted all his requests, for the hand of the LORD was on him.

“Many years later, during the reign of Artaxerxes king of Persia, Ezra son of Seraiah, the son of Azariah, the son of Hilkiah,”— Ezra 7:1 (BSB)