I will prepare destroyers against you: For prepare see 6.4. In the context you refers back to “house of the king of Judah” (that is, the royal palace) of verse 6. Destroyers here refers to men or soldiers who will destroy the royal palace, as Good News Translation makes clear.

Each with his weapons; and they shall cut down your choicest cedars: The weapons with which they cut down its choicest cedars are axes, which some translators render as “tools,” and the cedars are the cedar pillars of the palace. New International Version, for example, has “cedar beams.” Cedars are not widely known, but translators can borrow the term, as for example, in “beams [or, pillars] made from trees called cedar.” Or they can use a general term, as in “pillars made from the beautiful trees of Lebanon.”

And cast them into the fire refers to the fire of the burning city. We may translate “and set them on fire.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .