Firefox may ask if you want to import bookmarks from another browser when you first install it, but I think in other cases you would need to do it manually. Where are you getting cookies from? Internet Explorer (Windows Favorites), Edge, Chrome? Somewhere else? Or maybe: If you signed in to a Firefox Account, and Sync is enabled for Bookmarks, you can expect your Bookmarks to be shared across browsers in the account. See: [[How do I choose what information to sync on Firefox?]]