MR-J2-B is an SSCNET servo. Nobody but Mitsubishi offers SSCNET. You need to use it with an older Mitsubishi motion controller.
If it was an MR-J2-A it would be a standard pulse train, and it could connect to any controller capable of a high speed pulse output.
Either way, MR-J2-B is obsolete, replaced by MR-J2S-B, and now by MR-J3-B.