Well the ending -vich and its variations is used in a patronymic (= the son of) but it is also an ending of a surname - Petkevich, Petroshkevich, etc. So Grodno State archive might throw some light on Prokop if you come up with a few more details - like place of birth. I suspect that immigration form must list some locations in then Grodno Gubernia. Any materials in Russian left?
A