On a 1997 Ford F-Series truck with the 7.3L Power Stroke diesel engine, the fuel filter is located
on the driver's side of the engine, towards the front. It's usually mounted on the frame rail, near the engine's fuel injection pump. It's a fairly large, cylindrical filter. You'll likely see fuel lines connected to it.
However, a visual confirmation is always best. Consult a repair manual or use online images of a 1997 7.3L Power Stroke engine bay to be absolutely certain.
