If the pond is lined, filtered, and cycled, you can add the fish to the pond. Be sure the pond is covered with metal netting so predators like raccoons and herons can't get to the fish. There should be no sharp rocks around or inside the pond, and it should be in an area where no fertilizers, pesticides or herbicides can leach into it.
You can fit 10-12 goldfish in a pond that size.