Look for a white plastic container just like your wiper flood reservoir that will be the anti-freeze coolant container , it has marking on it , one of them says cold level that means when engine is cold that is the max level it should be at , other is the hot level and never open the rad or over flow container cap when any engine is hot it's extremely dangerous.
What I'd do if I were you is buy an anti-freeze tester from walmart etc for about 7 bucks and with the engine off and cold remove the over flow cap and pump the coolant up into the tester , check what it says so what temperatures its good for etc , go by the info in the owners manual or make sure it's not mixed more then 50/50 and if you add just water add distilled water.
What I do when buying any used vehicle is go over it head to toe , plus I change the gas , oil , transmission filters and fluids , plus I check and replace thermostats and coolants , also check the engine, transmission , rad , hoses etc for leaks and look the whole brake system and front end over , all belts etc too.
Hope that helps and best of luck.By the way check for any factory or service bulletins issues and for any program or flash updates via the dealerships.
