There is a feature request for this https://forum.obsidian.md/t/find-orphan-notes/817
So it’s easy enough to search for files that don’t have forelinks - they don’t have [[]]. Someone shared the regex for this https://forum.obsidian.md/t/searching-for-notes-without-links-orphaned-notes/3874.
To search for files that don’t have backlinks would mean searching your entire vault to make sure there aren’t instances of [[note name]] or whatever link format you are using.
This could be scripted. I couldn’t find anything on the forum, but I guess someone has already created this.