This assembly circulates room air through a vent in the fireplace, around the firebox wall and forces heated air back into the room.
You can call a heating contractor. If you plan on doing it yourself then you would have to dissassemble or remove the motor and assembly and take it to an electric motor supply place so that they can match it . There are probale some specs ingraved on the body of the motor.
Find the power cord and follow it. Hope this helps!