However, it's not a standard fuse. The blower motor often has its own circuit breaker or a relay instead of a standard fuse. Therefore, simply checking fuses in the interior panel might not solve the problem.
To be sure, you need to consult your owner's manual. The manual will have a diagram showing the location of all fuses and relays, specifically identifying which one is for the blower motor. If you don't have the manual, you can often find a PDF version online by searching for "1998 Pontiac Grand Prix owner's manual."
Failing that, you might consider taking your car to a mechanic or auto parts store for assistance. They will have the proper diagrams and can quickly locate the problem.