Bulk conversion in Calibre

I have been attempting to figure out a way to bulk convert my books into mobi format inside Calibre itself. I would like to do it there rather than using an outside script so the database will be in synch with what is in place. I simply cannot figure out how to sort the books so that all books with format != MOBI are displayed. I dont want to dupe stuff that I have already converted, or make the ORIGIONAL_MOBI stuff.

Any suggestions on what I am missing?

formats:"!=MOBI" does not suppress the matching books in the listing when I do a search..