You need to know load capacity and the type of transfer switch - built into the load center or external, automatic or manual, interlock to prevent backfeed…too many variables. Plus, the generator input should not be live when the transfer switch is set for service from the pole.
I suspect with a 4 pin inlet there is a ganged 30amp breaker at the transfer switch for 60amp service from the generator - if it was actually a whole house generator. Pictures, you need pictures of the input, transfer switch and generator service breakers.
If that input is no longer used then the safest thing to do is take the existing wires and wire in new 30 or 50amp service from the load center to the appropriate 30 or 50amp RV receptacle.
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