It has threads and it looks like a notch area on the threads is this the size hole I need? If so then I have about 2 turns to turn and tighten the mount!!
Do you know if it's a ground plane antenna or a zero ground plane antenna? Depending which type it is will tell you where you should mount it. If it's a ground plane you will want to mount it in the center of your roof so you get the best reception possible. It should only require about a 3/8 hole in the roof to mount it.