There isn't a single, universally located "fuel cut-off switch" on a Chevy S10 like you might find on some other vehicles (e.g., a readily accessible switch in the cab). Fuel delivery is typically controlled by the fuel pump, which is electronically managed by the vehicle's computer system. To stop fuel flow, you'd need to disable the fuel pump itself (a more involved process), or disconnect the battery.
Some aftermarket fuel cut-off switches *can* be installed, but they're not standard equipment. Their location would depend entirely on where the installer chose to place them.
