I have a '91 GMC S15 which is basically the same as the Chevy S10 of the same year. The filter is located on the frame rail directly beneath the driver's seat. Knowing the year of your pickup would help immensely in providing a specific answer to your question.
Were is the fuel pump in a 1985 chevy s10
I had a truck like that and the filter actually was inside the gas tank. you can call kragens. they can also help good luck