Your treadmill workout will include 20 minutes or more of hill climbing. Since treadmills are all different I'd like you to discover the level of incline intensity that you can successfully walk for the amount of time (10, 20, 30 minutes) you have set aside. If this is being done as a warmup, minimum of 5-6 minutes please. If sustaining the level of incline becomes too hard, back off of the incline for a bit as you recover. However, having spent time on a 30 degree treadmill and guessing your max incline is about 10, I think you'll find you can manage.