I'm not familiar with your specific model, but on the 3 trailers I've had the water pump has always been located near where your water connection to the trailer is. Usually you will have to remove some type of screw-on panel to attain access.
Look inside near where you fill your fresh water tank. On my 240 BHSL it is right under the kitchen sink. If I remove the drawer under the oven I see the water pump.
It is probably very close to the fresh water tank fill.