Light bar screws

I am trying to find the size of the small screws that surround the entire cover. I'm just trying to get a generalized idea incase I have to tap new ones.
BTW I have no idea what brand it is. I just got it off a used car because it didn't work. All it was was a bad relay. There is no name on it anywhere. All I know that it is a curved 52"
Thank you

A ruler or caliper should give you length.

For diameter/thread, I'd say pull one out, take it to Home Depot or Lowes, and head for the "nuts and screws" aisle - they have gizmos hanging up in there that are for determining size/thread of bolts or nuts. Whichever hole it threads into securely but without binding (be gentle so you don't jam it in or cross-thread it), should be the right one.