i have a 1991 buick regal 3800 were is fuel pump located

Start with the fuel pump relay, make sure it's good. (to test it, swap in a relay from one of the other spots in the fuse box). When you turn the car to ON you should hear the fuel pump priming. If you hear that then at least you know it's getting power. A fuel pressure test will let you know if there is a problem with fuel delivery. If you do anything to the fuel pump be sure to replace the fuel filter as well.

This does not tell you were the fuel pump is located at.