I don't have Video Easy to test, but the Magix web documents don't describe imports from DVD as a regular option. I'd guess you can do so if you change the extensions. VOB files are MPG format files, usually of a fixed maximum size for DVD burning, and they should work OK if renamed as .MPGs.
The IFO files hold the data for creating the DVD menu structure and almost certainly can't be used. You can create new menus within Video Easy though they may lack some of the fancy features of commercial discs. For info, single purpose DVD menu creation programs are available and they are expen$ive! BUPs are backup files in case an IFO gets damaged by scratching the disc etc.