The fuel filter is part of the fuel pump module inside the fuel tank. Nissan hasn't used an inline fuel filter in the Altima since 2001 and 1993 through 2001 were all located in the engine compartment. That's likely why you are having so much trouble finding a part number. Your best bet would be to provide a picture of what you are talking about. The only think I can think of near the wheel would be the evaporative emission system canister near the left-rear wheel:
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