Possible meanings are 1) This happened in the twelfth year after the Babylonians took the Israelites to Babylon or 2) this happened in the twelfth year after the Babylonians took Jehoiachin to Babylon. (See: [[rc://en/ta/man/translate/figs-explicit]])
This is an idiom that is used to introduce something that God told his prophets or his people. See how you translated this in [Ezekiel 3:16](../03/16.md). Alternate translation: "Yahweh spoke this message" or "Yahweh spoke these words" (See: [[rc://en/ta/man/translate/figs-idiom]])