Do I bake or broil if I am trying to cook a rack of lamb in a convection oven? And for how long?

I followed the directions on the lamb rack i got from the butcher that said to cook it for 30-35 minutes. I ended up putting it on bake(since it didnt say whether to bake or broil) for 55 minutes and it STILL isnt done yet!! Not even CLOSE to being done. Please help me! I dont know how to cook with this stupid convection oven ugh!