Are you looking to buy a new one? Just ask the dealer. Or if used, just ask the owner, they will know these better.
The batteries will do as others have indicated. They will run the fridge between campgrounds where you plug in and then it runs off shoreline 120 voltage.
With new batteries you may run it 2-3 days off battery depending on how much other power you use for lights/fans/electronics etc.
Manufacturers are notorious for putting in the wrong batteries. RV/Marine batteries are ALWAYS the WRONG battery for an RV. "Marine" batteries are only for boats or similar applications, not for running a camper.
Get GOLF CART batteries if going the flooded style, or upgrade to other types.
IF you plan to travel from home straight to a camp ground then back then your battery needs will be very minimal, almost just for emergency uses or during the drive between plugging in to an outlet.
If you plan to camp off-grid with no hook-ups then you will need either a loud generator running half the time or to use solar to keep the batteries charged. 200 watts minimum. 300-400 if you have room on the roof.
Yes, putting flat solar panels on the Airstream is cringe-worthy, but you must in some situations.
I suggest to never use those flexible panels, and several reasons not to. Use the flat glass panels if at all possible.
The deployable "suitcase" or portable solar panels will work, but are a lot of work and only work when they are deployed and plugged in; roof-top panels are always working in the sun, you will need them to always work.
Your fridge will either be an absorption (propane 3-way) or a Danfoss style compressor electric (that needs no outside ventilation). The manufacturer will not install anything except these two options. If buying used from a cheapskate or very ignorant owner then you might get stuck with a household residential style refrigerator. There are some situations where these would be useful and desired, but in general for camping they are not the right way to go.
