Someone up-thread posted a photo of a standard triple park outlet box.
Parks will, depending on the prak have either boxes like that, Boxes with only the two right hand outlets or boxes with just one of the two right hand outlets.
The one on the left (has 3 flat slots and one round or "D" or "U" shaped slot) is 50 amps at 120/240 volts This is for a 50 amp rig.. More on that in a bit.
The other two are 120 volt (30 and 15/20 amp respectively.. I suspect your rig is one of those.
Plug into the outlet that matches your plug.. That simple.
I do recommend measuring voltage BEFORE you plug in (Some parks .. weird things happen)
If you have a 30 amp rig and get in a park with only 50 amp outlets.. Get a dogbone adapter (This has a 50 amp plug and a 30 amp outlet with a short cord between them) it handles everything, again MEASURE before pluging in rv though.
The major danger with 30 amp rigs is "other than RV park" 30 amp outlets. Example you hire Joe the electrician, tell him it's for your RV, he puts in the TT-30 outlet (Which is clearly marked 125 volt max) and wires it for 240 volts cause HE sees a dryer or air compressor or welder outlet, not an RV outlet like you told him.
Or pluggin in at a friend's or a shop or somewhere else wher eit's a 240 volt outlet.
If you have JOE (Generic name) install an outlet for you.. Get a 50 amp. Safer that way, less chance of a screw up.