Yes. You can drill almost any area as long as you check to make sure there is no equipment etc where you want to drill. It sounds like you want to go out through the storage area floor, and back up into the under bed area?

Knowing the "why" may get you more, focused help.

Is this for use at your home or at campgrounds? If at home, I think you would be better served by installing a 30A RV outlet and using your regular power cable. That is what I did. I installed the outlet next to the outside main breaker panel and use a 50' extension to get power to my R-Pod. Instead of running a 20A power cord from a post into the R-Pod through the wall, why not just use an adapter with your 30A cable to plug into the 20A outlet if that is all you have. Is this to run a separate 20A circuit into the R-Pod?

I don't know what you would need it for, but placement of a hole is conditioned on missing any support members. On a cold, humid day you may be able to see where the framing members are located. Mark a suitable spot if you are going to run it through the wall. On the slide side, that would bring it into the same compartment as the furnace and water heater. It might be easiest to use the wall and a covered connector (like the 30A connector uses) for your connection. I don't think running through the floor is a good idea. I think it would be harder to seal against road spray when wet and your connector would be more vulnerable to corrosion. Just having a hole through the floor through which you could stick a cord is not a great idea. It would be an opening for water to get in and cause all kinds of damage. However, it is your 'Pod, and you can do as you wish with it.