Whom did God tell Moses to bring, with his sons, to serve Him as priests?

Answer: Aaron

God told Moses to bring his brother Aaron and Aaron's sons Nadab, Abihu, Eleazar, and Ithamar to serve as priests.

““Next, have your brother Aaron brought to you from among the Israelites, along with his sons Nadab, Abihu, Eleazar, and Ithamar, to serve Me as priests.”— Exodus 28:1 (BSB)