^^^^^
A single panel with MC4 connectors.... just get an MC4 connector cable. Cut in half so the connectors snap onto the panel and the cut ends hit the controller. Generally it is #10 wire.
If panels are parallel you can buy some MC4 connectors to two panels. That is about max for #10 wire to the controller. Although voltage drop is not a huge deal as the controller clips voltage to the charging level anyway. For more in parallel it is probably best to tie them tegether in a combiner box and use larger wire to the controller.
With series the same cable can be used. No practical limit on RV panels but you will need the proper controller for the high voltage.