OET interlinear HERO (JDG) 4:3

uW Translation Notes:

Note 1 topic: writing-pronouns

כִּ֠י תְּשַׁ֨ע מֵא֤וֹת רֶֽכֶב־בַּרְזֶל֙ ל֔⁠וֹ

(Some words not found in UHB: and,they_cried_out sons_of Yisrael to/towards YHWH that/for/because/then/when nine hundreds chariots_of iron to=him/it and=he oppressed DOM sons_of Yisrael by,force twenty year )

The pronouns him and he seem to refer to Sisera, since these chariots were under his command. Alternate translation: [because Sisera had 900 iron chariots]

Note 2 topic: figures-of-speech / explicit

רֶֽכֶב־בַּרְזֶל֙

chariots_of (Some words not found in UHB: and,they_cried_out sons_of Yisrael to/towards YHWH that/for/because/then/when nine hundreds chariots_of iron to=him/it and=he oppressed DOM sons_of Yisrael by,force twenty year )

See how you translated the same expression in 1:19. Alternate translation: [chariots fitted out with iron]

Note 3 topic: figures-of-speech / abstractnouns

בְּ⁠חָזְקָ֖ה

(Some words not found in UHB: and,they_cried_out sons_of Yisrael to/towards YHWH that/for/because/then/when nine hundreds chariots_of iron to=him/it and=he oppressed DOM sons_of Yisrael by,force twenty year )

If your language does not use an abstract noun for the idea of might, you could express the same idea in another way. Alternate translation: [mightily]