I bought a MKII pump that comes with a three pronged plug. I want to connect it to a switch so I have better control. So, when I cut the plug off, I’m a little afraid of what I’ll find. I doubt if the wires come sheathed in black, white and green coverings. How will I know which wire is the ground ( I’m assuming the other two wires are interchangeable, hot and neutral). I’d appreciate any advice.