objects1 is an old file, now redundant. If you want to play an old mission that uses it, you'll have to get your editing hat on.
Open the misson.sqm in Wordpad or Notepad. Examine the various addon sections at the top and at the start of the Intro and Outro sections. Remove all references to objects1 and save. With luck, the mission might now work.
I use Kegetys' OFP launcher (grab it from his site) in combination with my mod folders. I have official addons only in my actual addons folder, then I have a mod folder which I call "standard" which contains a few standard addons like this.
To make it work with a full blown mod like FDF, which uses its own .exe, you probably have to put it in the FDF addons folder. Not sure.