The inertia switch is the closest thing to a "safety shutoff" and is usually located under the dash, often under the carpet near the driver's side. However, it's not a switch you'd normally use to manually stop the fuel pump unless you suspect it's malfunctioning and suspect a collision has tripped it.
To be certain of its location on *your* specific 1996 Plymouth Breeze, consult your owner's manual or a repair manual specific to that year and model. A search online for "1996 Plymouth Breeze inertia switch location" might also yield helpful images or diagrams.