Final Cut Pro user group for North of England
I have to ask immediately, of course, if you own the copyright to these DVDs? If you don't I won't be able to tell you how on this forum as I can't endorse copyright infringement.
But if you are working legally, try MPGStreamclip to process the .VOBs of the Video_TS folder.
Everything in FCP should be Quicktime medi, so that's what you are aiming for.
Let me know what it is you are trying to demux?