Comment by briHass

Have you tried the Import plugin in Obsidian? I used it the other day, and it seemed to do a good job with OneNote, though my ON notebooks are just simple text and images. I believe it automates an export from ON to HTML and then converts that to MD.

Once they're in MD format, you can always get your favorite agent to do more formatting and organization, which was one of the big reasons I moved away from ON.