The year and Model of your Montana is essential to figuring out where your power plugs in.
The key here is you need a power cord which I suspicion you don't have? The usual one is a 50 amp male plug on one and and a round twist-to-lock marine type 50 amp female. Be aware (as posted above) this is *NOT* a 240 volt 50 amp system. it is two legs of 120V 50 amp power. The wiring at the supply point needs to be correct for an RV (or bad things happen).
You probably won't have a 50 amp supply and will need to adapt the power cord to a lesser amperage supply (120V at 10, 20 or 20 amps). There are adapters you can buy to connect them to your 50 amp cord. Amazon has many different adapters.
https://www.amazon.com/s?k=rv+power+...l_3t4dbjixtr_e