I can’t say with certainty for your 310RL but on my 340RL, they are on the off-door side, behind the rear tire next to the I-beam. Red and Blue PEX lines dropping down from the underbelly terminating in white valves.
On my 310RL, there Is a 2” fresh water dump gate valve and a single Low Point Drain with a valve, both are located just behind the wheels on the drivers side.