Do as BurbMan said. Install a true 30 amp RV outlet and run a true RV 30 amp extension cord from the outlet to your camper.
I ran my camper at home on a 20 amp receptacle for years (plug outside the house). And even ran an orange construction style 100 foot electric cord from the receptacle to the camper and it worked fine for years that way. I could even run the air conditioner, but the orange cord would get warm after a while.
In time, I finally installed a 30 amp RV receptacle and a few years later decided to park the camper a different direction, so installed the second one at a different location, along with replacing a 20 am receptacle that use to exist on a basket ball hoop pole. With options now, I never have to drive over the RV extension cord, wherever it's parked. And I can run the air conditioner any time, and actually live in the camper (which we do most of the summer months).
Install a real RV receptacle with a dedicated line to your breaker box and dedicated breaker for that one line only. Then you have all kinds of options what you plug into it, and you're not breaking any building codes or raising alarms when neighbors see wires laying in your yard.
If you look under the window of the garage, this was my first attempt at putting a receptical on the outside of the garage. We use to park the camper right here. I just tapped into a 20 amp plug on the other side of the wall. Worked OK for a long time that way.
Then, decided to do it right and installed a true 30 amp box (between the door and the front) of the garage, as that was the easiest way to run the wire from the breaker box inside the garage.
A couple years later, I added the box on the electric panel beside the garage. Total length of wire from the splitter box (200 amp, 100 to the house and 100 to the garage), it took about 3 feet of wire to install the RV box. I now have the outside 20 amp, and 2 outside 30 amp boxes. It all works well together. I actually can run a mini-campground now if I want!