I need to know the name of the cover that is metal with slats in it that goes over the burner and is the outside part for a central heat unit that is inside.

My best guess is the burner. Like number 41 OR heat exchanger but heat exchangers do not have slats.

I mean it goes to cover up all the inside parts but still allows air in because right now everything is exposed and the filter has a cover over it but the center part is missing.

Are you talking about the furnace cabinet? Find a picture on Google or take a picture of what you have . Guessing games never work well.

http://www.mobilehomedoctor.com/mobile-home-furnace-pictures.htm scrolling down I see it shows the six picture or 2nd one from the bottom all the inside is exposed and is it the cover plate the metal to the right is what is off or does it have another name?

Second picture from bottom is burner line,or gas train line,or burner manifold. Like I said before find a pic on Google and post it.