I hope it's still early enough, I have several I plan on replanting this fall and haven't started on it yet! They should be mulched after transplanting, but this is the time temperatures drop enough that hellebores start to grow again after their summer rest.

The best time to do this is immediately after the bloom cycle....same with dividing. You can transplant now but there is a likelihood you may impact the flowering as well as the possibility of insufficient time for the plants to settle in and the roots start establishing before cold weather hits.