Here the "cities of Judah" represents the people who live in them. Alternate translation: "The people who live in the cities of Judah and in Jerusalem" (See: [[rc://en/ta/man/translate/figs-metonymy]])
This can be stated in active form. Alternate translation: "but their gods will certainly not save them" (See: [[rc://en/ta/man/translate/figs-activepassive]])