RobH_en_tn/jer/50/04.md

In those days and at that time

These phrases mean the same thing and emphasize the importance of that future time. See how you translated this in Jeremiah 33:15. (See: rc://en/ta/man/translate/figs-doublet)

this is Yahweh's declaration

Yahweh speaks of himself by name to express the certainty of what he is declaring. See how you translated this in Jeremiah 1:8. Alternate translation: "this is what Yahweh declares" or "this is what I, Yahweh, declare" (See: rc://en/ta/man/translate/figs-123person)

seek Yahweh their God

Seeking Yahweh their God represents either 1) asking God for help or 2) thinking about God and obeying him. (See: rc://en/ta/man/translate/figs-metaphor)