A three phase 1 HP is very rare. With three phase you have a 50/50 chance that it is running backwards. There may not be much difference in amperage, and it will pump some water and pressure running backwards. But there should be a measurable difference in flow and pressure between running backwards and forwards. It doesn’t hurt the pump to run backwards for a short time. So the best way is to run it one way, swap two wires and run it the other way, and see which way it pumps the most water and pressure.