Not enough information provided to know for sure. Usually it's the fuel pump elbow molded into the pump module that leaks fuel on to the tank and manifests as a stain on the bottom, in addition to the smell of fuel. Do you know for sure you have a hole in the tank, or have you noticed there is a leak and assumed there is a hole in the tank?
If it turns out there is indeed a puncture in the tank and mileage is sufficiently high (near 100k miles) you should replace the pump as preventive maintenance along with the tank.
Should be on the passenger side. Look under the car at the bottom of the tank on that side, you should see staining on the bottom of the tank from the dust and dirt that flares up before it dries and sticks to the tank. Like the 3.6L timing chains, this is an all too common problem across several GM vehicles.