Inverter draw from battery for residential fridge

look at the fridge nameplate and look for either the power in watts or max current. If it lists max current multiply by 10 to get inverter draw from 12V

If it lists watts current =watts/12

that will give you a pretty close estimate of max power draw from the batteries.

now to get run time you will need to take into account the duty cycle of the fridge, what % of the time the compressor is running.