I would say you could turn it on and open a faucet and listen for the racket. That is one way if I didn't know where it was located. I found mine by the noise. lol
You may have to remove a few screws to remove a panel. The pump maybe under the frig, or under a dinette seat. Look for areas that have "dead" space that you cannot easily get to. The pump usually is within a foot or two of the water storage tank.