OET interlinear YIR (JER) 50:30

uW Translation Notes:

(Occurrence 0) her young men will fall

(Some words not found in UHB: for=so/thus/hence fall men_of,its_young in,its_open_of,places and=all men_of its_war_of,her perish in_the=day (the)=that declares_of YHWH )

Alternate translation: [they will kill her young men]

Note 1 topic: figures-of-speech / activepassive

(Occurrence 0) all her fighting men will be destroyed

(Some words not found in UHB: for=so/thus/hence fall men_of,its_young in,its_open_of,places and=all men_of its_war_of,her perish in_the=day (the)=that declares_of YHWH )

If your language does not use the passive form in this way, you can state this in active form or in another way that is natural in your language. Alternate translation: [I will destroy all her fighting men]

Note 2 topic: figures-of-speech / 123person

(Occurrence 0) this is Yahweh’s declaration

(Some words not found in UHB: for=so/thus/hence fall men_of,its_young in,its_open_of,places and=all men_of its_war_of,her perish in_the=day (the)=that declares_of YHWH )

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]