For moving bookmarks to another computer see.

• Export Firefox bookmarks to an HTML file to back up or transfer bookmarks

OR

• Restore bookmarks from backup or move them to another computer

When deciding whether to export and import an bookmarks.HTML file , or to use a JSON bookmarks backup file to "restore" ...

The JSON files contain your Tags, but don't contain the individual images (Favicons) for bookmarks. JSON also overwrites any existing bookmarks in the target Firefox installation.

The HTML file type has the Favicons for your bookmarks, but doesn't contain any Tag data. The HTML file type appends existing bookmarks.