Lug pattern for after market rims

Okay, how do I tell what kind of truclients I have? Listed above is the truck I have, it is an extended cab 4x4. I am trying to buy some after market rims and do not know the exact lug pattern, it is six lug. How do I measure the rest and buy the rims? They have a few options like DXL extended cab 3.4l v6 and SR5 extended cab 3.4l v6 and a base extended cab 3.4l v6 and a regular extended cab 3.4l v6. It does not give a 4x4 option. So how do I tell which one I have? Please help and how do I measure my lug pattern? Thank you.