If you have an assembly manual, it is in there, pg 442.
If you don't have an assembly manual, here is the location of the button per the illustration. The location of the button is on the RIGHT side of the glovebox. From the bottom of the opening, measure UP 2 9/32in. From the back surface of the box, measure FORWARD 6 21/32in. The hole is shown to be 9/16, but I would strongly recommend that you start out with a smaller hole and work up to a size which fits. The original push button was green but the one that is still available from GM is a yellow button, which will work fine. The yellow button is the type which is pushed into the hole. The button has two terminals. One goes to the solenoid connector in the trunk and the other goes to the fuse block at a "BAT" terminal.
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Tom Parsons