OK, your Air Flow is Over 750 CFM.

You can purchase the 13F filters HERE.  You will need One filter for every 750 CFM.  (A 1,500 cfm system will need 2 filters…)

To attach the fan to the filters you will build a plenum that looks like this:

 

…or like this:

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(You can use your Back button to return to the previous screen.)