Hi Tessie, I am only guessing here,
but I would say maybe an hour and a half at 350. I would put the racks in the center of the oven, then place one lasagna to the far left on the top rack, and the other to the far right on the bottom rack, then switch them about half way through the cooking time. I would check them after about an hour and see how they look. You will want to uncover them for the last 10-15 minutes. I hope this helps!