If your shop and your house are two separate buildings, and the only electrically conductive path between them is the ungrounded feeder, then your ungrounded feeder is OK to continue using. If you have a communications cable (phone, TV, network) or a metallic water line or anything like that connecting them, then you need to install a modern feeder with grounding conductor.
In either case, you need a grounding electrode system at your barn, which if it is only ground rods needs to be 2 grounds rods. But if you have a concrete encased electrode (UFER) that would suffice. You need a main disconnect at the point the feeder enters the building. If the feeder is ungrounded, then your barn EGC system starts there, and you bond together your barn EGCs, the grounding electrode system, and the feeder neutral. Whereas if your feeder has a grounding conductor, then you tie together your barn EGCs and the grounding electrode system with the feeder EGC, and none of those connect to the feeder neutral.
Very important and so worth repeating: if you have an ungrounded feeder, then your ground and neutral in the barn need to be bonded together at the main disconnect. Otherwise a hot to EGC short will not trip a breaker.
Cheers, Wayne