I haven't used or needed to used this format . . .
However . . . your question has aroused my interest!
Now, as far as I have read, OGM
is part of of the Ogg Vorbis process.
This produces OGG files, and that, I believe, from seeing the Media Files available. we can import.
OK . .
But you have an OGM - hmmm... I wonder what would happen IF you were to change the file extension to OGG? And then try? MAKE A COPY OF THE ORIGINAL FIRST and use that!!! Here is something ELSE I've picked up to support our quest - to do with rendering but kinda puts Ogg Vorbis in the "
Pantheon of Vegas Templates"

and it is this :"
Vegas has its own plug-in that was built using the Ogg Vorbis SDK, there is nothing that you need to install. Just select Ogg Vorbis from the format dropdown in the Render As dialog."
Now, and I haven't done this, to PLAY OGM, that wonderful Swiss Army Knife of readers -
VLC - free for downloading, GET IT - will read OGM files. So that's a help too!
And again, here is a "
converter" which I have found but haven't used, that is supposed to convert OGM to AVI.
Convert OGM to AVI, OGM to DivX, OGM to xvid, OGM to AVI Converter Download
Here is the Vorbis site:
Vorbis.com
Thanks for pricking my interest neurones!
Grazie