I'm not familiar with your camper but, normally, it's located underneath the mattress. (In it's own compartment or easily accessible from underneath in a storage place.)
And easy way to find it is to turn on your water pump and run a faucet...and let your ears guide you!
With my old camper, the BEST thing I ever did was install a winterization kit...made the job super easy.
Here's what a typical water pump looks like:
Here's what the winterizing bypass kit does...you just put the valve on the line that comes from out outside water input...when you switch the valve, it pulls from the tube that you have inside the antifreeze jug to fill the lines/faucets with antifreeze.