You cannot "convert" 9 amps in watts. Amps are a unit of electric current, and watts are a unit of electric power. Power is given by P = IV where P is power, I is current and V is voltage. To...
1 Horsepower is about 746 watts. So 1/2 HP = 373 watts. The actual power drawn from the source is probably more than that due to reactive power, winding resistance and friction, to name a few factors.