Where were the people of Judah taken captive?

Answer: Babylon

Nebuchadnezzar carried King Jehoiachin and Jerusalem's leaders into exile to Babylon; later, those who escaped the sword were also taken there.

“Nebuchadnezzar carried away Jehoiachin to Babylon, as well as the king’s mother, his wives, his officials, and the leading men of the land. He took them into exile from Jerusalem to Babylon.”— 2 Kings 24:15 (BSB)