Hey, bees have moved into my abandon beehive, …

Hey, bees have moved into my abandon beehive, and I'm going to open it up today and check them out and take out any debris and nasty bugs and probably do a treatment for varroa before they get totally settled. But I was wondering if you had any tips on locating the queen? Because if I don't have a queen in there I'll have to buy one lol

Pull out the middle frames first (or wherever the middle of their cluster is.) Typically she’ll be there if she’s in there.
Though if you can’t find her visually, just look for eggs in the cells. Usually eggs are a good sign that a queen is present and healthy. ^^