Here you go. You can see the ground tab is on the side of the twistlock, and you will also have a corresponding tab inside your receptacle on the RV.
Looking at the 50A 3-prong locking pic....The X and Y are your 120 volt legs, the W is your neutral, and the G is your ground on the side.
2011 Flagstaff 831 RLBSS
I used to be addicted to time travel, but that's all in the past now.