en_tn_condensed/jer/50/30.md

her young men will fall

"they will kill her young men"

all her fighting men will be destroyed

This can be stated in active form. Alternate translation: "I will destroy all her fighting men" (See: rc://en/ta/man/translate/figs-activepassive)

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)