After God brought Manasseh back to Jerusalem, what did he do with the foreign gods?

Answer: Removed them from the temple

The humbled Manasseh removed the foreign gods and the idol from the temple, restored the LORD's altar and told Judah to serve the LORD.

“After this, Manasseh rebuilt the outer wall of the City of David from west of Gihon in the valley to the entrance of the Fish Gate, and he brought it around the hill of Ophel and heightened it considerably. He also stationed military commanders in all the fortified cities of Judah.”— 2 Chronicles 33:14 (BSB)