Your best bet is to consult your owner's manual. It will have a diagram showing the location of all fuses and relays, including those for the airbag supplemental restraint system (SRS). The manual will also indicate the amperage of the fuse(s) involved.
If you don't have the owner's manual, you can often find a digital version online through the GMC website or a reputable automotive repair manual provider. Searching for "2000 GMC Sierra owner's manual PDF" should yield results.
Important Safety Note: Working with the airbag system is dangerous. If you suspect a problem with your airbags, it's best to take your vehicle to a qualified mechanic. Improperly handling the airbag system could lead to accidental deployment and serious injury.