What size tires do i need for Lincoln Navigator?

I have a 2001 Lincoln Navigator, with 22' rims. I need new tires, but do not know what size, or tread or whatever that i need. Does anyone know or at least have an idea of what i am looking for? I am a 25 year old woman... i love the way my truck looks, but dont know much about it, except how to drive it. Thank you!