Easiest solution. Get a matching Generator adapter.
But first some questions....
Is that plug 3 or 4 Slot.. (Get an adapter with a matching plug)
IF it is 4 slot great, You can likely get a "Generator to 50 amp RV" adapter. then test it BEFORE you plug in, or better yet plug in a Progressive Industries PT-50C (Or hard wire a HW 50 c for the best solution) assuming your RV is 50 amp, if it is 30 amp change 50 to 30 in the recommendation.
Now, if you have a 3-slot then you adapt to a TT-30 outlet.. But before you plug in (less you take the advice above about the PI priducts) take a volt meter and measure the voltage between teh two FLAT slits (Ignore the round hole for the moment) 120 volts.. GOOD, 240.. Bad
Now one of those flat blades should also show 120 to the round (The other zero)
IF so, good test, Next 30 amp test
Get a adapter with a TT-30 plug and a 15 amp outlet
Get a 3-light Outlet tester
Plug the second into the 1st into the outlet
Proper light pattern = Good test.