Cargo Lamp Mounting Question

[72step]

I need to reinstall the cargo lamp on my truck, however, I've been putting it off because the cab, has these big holes with some sort of nut kinda sealed into the bigger hole, and on one side the nut is gone. What is the typical way these lights go on? Not sure if it was messed with by a previous owner, or if that's the way they go in? I might just drill a bigger hole into the cargo lamp housing and use a regular bolt and nut, but I hate to do that. Any ideas? Thanks.......