Behind the driver's seat there is a trunk release that works with the ignition key.
There is a manual release behind the rear seat, fold the seat down to find it, than have someone push the trunk release button. If this dose not work it may be broken.
Usually they are in the glove box, but they could be located on the floor, in front of the seat, on the drivers side, or on the drivers door itself. The 1998 Buick Regal unfortunately does not have a manual trunk release. There are kits available to add a manual trunk release, however.
Glove Box
Owner's manual or keep looking. Maybe it does not have one. Look at the trunk lock and see if it is manual or electric.
There is an auto trunk release on a 2004 Grand Prix. If you push the drivers side door lock button to the left and hold it, the trunk will open.
NO, only button it has is on remote and manual open on trunk door, when car is unlocked.
Look in your owners manual.
Check in the glove compartment.
Look in your owners manual and it should tell you.
Read your manual. There is a switch in the glove box to disable the trunk release button on the dash. you lock the glove box with the regular key. When you give someone the valet key they can not get in the trunk.
Beleave it or not; it's in the trunk Fuse panel. Look in owner's manual for location.