How do you find the GVWR in the VIN number?

Depends on the manufacturer. If it is in the VIN, it'll either be in positions 4 - 8 on the VIN, or possibly positions 11 - 17 - these are determined by the manufacturer, and what these positions actually mean depends on the manufacturer. We'd need more info about your vehicle to tell if that info is even in the VIN, let alone what it is.