I don't know if the formats are compatible or not, but your bookmarks are all stored in the firefox profile. So perhaps you can find your old profile, and copy it to the new location?

https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

That links to another page with a section specifically about restoring bookmarks after upgrading Windows 10...

https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them