them: i.e. your fathers.
it: i.e. the incense.
into His mind. upon His heart. Figure of speech Anthropopatheia..
Related Commentaries of Jeremiah 44:21
Jeremiah 44:21
21 The incense that ye burned in the cities of Judah, and in the streets of Jerusalem, ye, and your fathers, your kings, and your princes, and the people of the land, did not the LORD remember them, and came it not into his mind?