How many potatoes are in a 32 ounce bag of hash-browns?

This is a bit like asking how many sand come in a bag. How big a bag? What portion of sand constitutes "one sand"? One grain? One handful? Something else?

Bagged hash browns are usually sold by weight, so typical amounts would be something like "one pound" or "13.2 ounces" or something like that; look on the bag itself to see the net weight of the contents.

If you're talking about hash brown patties (where "one hash brown" means "one patty"), then again, consult the bag itself. You may have to read between the lines a little and look at the nutritional information, where it will probably say something like "Serving size: 1 patty" and "Servings per bag: 8.5".