I will be using a commercial convection oven to bake 70 potatoes wrapped in foil.  Can you advise me on the length of time and what temperature to set the oven on?  I know that it will take less time but do not know what temperature to set the oven?

As a general guide line with the convection oven you can bake the potatoes at 375 degrees F versus a higher temp in a conventional oven. Still, I have found 400 degrees F for 55-60 minutes works well and the potatoes are fully cooked when they reach 210 degrees F. I always try to place the potatoes in a single level on a sheet pan so seventy might take a couple of racks. This provides air circulation and more even cooking than baking lots of potatoes in a 4-6-inch-deep pan. The size of the potato can make a difference too, we usually say one hour for a 70 count potato, typically the same size as the loose potatoes at a grocery store. Smaller sizes take less, recently had one of our growers give a friend a couple of 2 pound each russets from Idaho, it took two hours to bake up dry and fluffy. So, larger sizes take longer than our "official" recommendation.

Not a fan of foil, as the russet potato from Idaho is about 80% water and so sealing up in aluminum foil yields a steamed, rather than baked end product. If you can, baked first then using an oven mitt, wrap in foil.

https://idahopotato.com/dr-potato/foil-baked-potatoes

https://idahopotato.com/dr-potato/why-i-do-not-recommend-baking-potatoes-in-aluminum-foil