Here the "tribes of Israel" refer to the people of Israel. Alternate translation: "help the people of Israel" (See: [[rc://en/ta/man/jit/figs-metonymy]])
The phrase "carry out" means to "serve." Alternate translation: "they must help the tribes of Israel by serving in the tabernacle" (See: [[rc://en/ta/man/jit/figs-idiom]])