The adapter to plug the RV into a 120v wall outlet is simple enough and readily available, e.g. the Walmart RV aisle, Amazon, RV parts stores, etc. The common on has a 30A female receptacle on one side and a 15A plug on the other. If you have a 50A RV, you also need a 50A female-to-30A male adapter, but you need one of those anyway. That gives enough power to run the battery charge system, though not much else.
I prefer the dogbone type (two ends and a short cord), but there are also the single module type.
https://www.homedepot.com/p/Conntek-...4200/308990717
https://www.walmart.com/ip/Camco-Pow...55233/23500635
It works pretty well at home but rather "iffy" for a storage facility, for several reasons:
1. The facility may not have outlets or allow you to plug to them
2. Other RV owners may be using them as well and can trip breakers while you are unaware.
3. Someone will accidentally or intentionally disconnect your plug.