OK, was that a DVD-Video, that you authored in your older PrE, with the VIDEO_TS folder, and the IFO, BUP and VOB files, or was it a DVD-Data disc, with an AV file on it?
If the latter, what is the format (file extension) and CODEC used in that AV file?
Also, if a DVD-Data, was it done on a Mac, or a PC?
Good luck, and let us know just a bit more, please,
Also, you mention DMG, which is a Mac Disk Image File.
If properly written, then the disk, containing that file, should Mount, just like a hard disk drive. Is that not happening on your Mac?
Also, I do not believe that PrE could write directly to a DMG, so if that is what you have, it might be useful to know exactly how that DMG file was created.
You definitely should not get a DMG file when you Publish & Share your movie!
A DMG is, as Bill says, a Disc Image File, the equivalent of a Windows ZIP file. It's usually used to deliver a program via download and should extract and launch (usually installing a program) automatically when you download it to your Mac.
I don't know any way you would have gotten a DMG file from a Premiere Elements video.