Your camper is wired for 50 amp service and someone has added an additional 20 amp circuit trying to get a total of 70 amps.
Your 20 amp wire's plug looks corroded (and unsafe) to me from the photo.
You need to find out where that added wire goes and if it has circuit protection in it.
To plug your 50 amp plug into the campground you will need a 50 amp service to 30 amp service adapter cord.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW