Hi, Firefox has two different bookmark transfer file formats with different feature names attached:

• JSON: "backup" and "restore"
• HTML: "export" and "import"

Since you create a JSON-format backup file, the corresponding feature to install your backups on your new installation of Firefox is the restore feature. More info in this article: Restore bookmarks from backup or move them to another computer.

Does that work?

Note that restoring a JSON backup will replace all existing bookmarks (you see a warning). If you already have created bookmarks that you want to keep then first create an HTML backup. Then you can import this HTML backup after you have restored the JSON backup.