How do you know if fuel filter is bad? on 2004 Kia Optima

Engine will turn over but car will not start. Not sure where the fuel filter is loacted. Found 3 filters, one in driver rear of car, and one under hood connected to possible fuel line to engine, and another to the right of engine. Checked all sensors and they look good.
Any suggestions?

Asked by for the 2004 Kia Optima
The fuel filter on the 04 Optima is part of the fuel sender unit in the fuel tank and is not really a serviceable item. A restricted fuel filter normally results on loss of top end power, and eventually can ruin the fuel pump as it causes the pump to work under duress.