Premiere Elements is a video editor and technically not a converter.
But you can certainly put VOB files into a Premiere Elements project and then output an mp4 from that project. (Assuming, of course, that these VOB files are not from a commercial, copy-protected DVD.
The exact instructions for doing this depend on which version of the program you're using.
If you provide Premiere Elements version and operating system in use, I will post in your thread detailed how to on using the DVD video files from your DVD-VIDEO standard or widescreen on DVD disc in your Premiere Elements project.
If you are using the newly released Premiere Elements 14, you will notice that the route to .mp4 will be markedly different than in earlier versions.
By the way, are the source DVD-VIDEO on DVD disc "DVD compliant" and have the frame size 720 x 480 or 720 x 576? And, where are these DVD video files now, still on the disc or as a bunch of VTS_01_1.VOB files and series copied from the original DVD-VIDEO on DVD disc and put on a DVD disc as data disc?
Please consider. If any questions or need clarification, please do not hesitate to ask. But, details are important to expedite matters.