Most 6" jointers only have a 1 hp motor, and it's usually capable of being wired for either 120 or 240v~. You may only need to swap around a couple wires within the motor, and put a new power cord on it. There's often/usually a motor wiring diagram on the underside of the cover, where the wires go into the motor. Check it out!
...Unless, of course, you mean that the current motor is three-phase... (Many commercial shops are.) In that case, you will need a new motor.