1993 Cadillac Fleetwood lost key

Easiest is to visit a GM dealership. The dealer that originally sold the car may still have the key code on file, otherwise they can get it from GM or they can take a lock cylinder apart to measure the tumblers, and cut a key from that.

Ok . and I know it has the key with the chip in it.

Unless you have an old key to measure the pellet, you are likely going to have to change the Passkey Module also. There is no way to determine which value it is using. A new module will be neutral until a key code is sent to it.