Put water in your fresh water tank, turn on and listen. Follow the sound. Until you modify the pump it will be loud enough to hear. Should you eventually wish to quiet it, a flexible hose and foam base will help. I insulated all my lines in pipe foam as well. Makes a difference for sound.
Mine was behind a thin piece of panel held in place by a screw just inside the back door. Probably very close to and above your fresh water tank.
And If you turn it on and the lines are pressurized you may have to open a tap to get it to start as it will turn on and off with the pressure in your lines.