To be absolutely certain, consult your owner's manual. It will have a diagram showing the exact location. If you don't have the manual, you can often find a digital version online through a search like "1997 Chevy Blazer owner's manual PDF".
Failing that, a visual inspection along the passenger side frame rail near the fuel tank is your best bet. Look for a cylindrical canister with fuel lines connected. Be cautious when inspecting, as you'll be working near fuel lines.