Don't be embarrassed Joseph - there are absolutely no need for you to be embarrassed at all. This is to most friendly forum and helpful forum "in cyberspace". I have asked a very large number of questions where the answer I am sure seems obvious to a lot of seasoned RVers, and never once have anyone made me feel embarrassed (except for close friends who would take the opportunity to laugh at me any way)
I also strongly suspect that there are no "main filter" in your RV. Our 2007 Monaco Diplomat didn't come with one, and I think only the really "high end RV's" has one that is factory installed. If you think you need one, there are a variety of filter options that are installed outside your RV.