I'm heating a ham in the oven at 250°F. How long will it take to cook baked potatoes at the same time?

The more things you put in the oven and the larger they are, the longer it will take. I’d allow two hours for the potatoes to cook and if they’re not fully done at the end of that, you can always put them in the microwave to finish.

https://idahopotato.com/dr-potato/what-is-the-baking-time-of-an-idaho-potato-at-250-degrees