Sync isn't for backups, it's used to sync between device to sync server back to device. The original data will always be on the computer it was created on you only get a sync but if the main computer is gone the data will also go with the computer as well. So you need to be sure the original computer is still work and connected but then we you do you will have to use the Firefox FAQ for data backup to import to the new computer setup so that the data will not be lost.

Let's start with bookmarks. The typical methods of access are:

• Toolbar - this is a horizontal bar below the main toolbar. See: Bookmarks Toolbar - Display your favorite websites at the top of the Firefox window
• Sidebar - this is a panel at the left or right side that can show bookmarks, history, add-on pages, etc. See: Use the sidebar to access tools and vertical tabs
• Menu bar - this classic bar with File, Edit, View, History, Bookmarks, etc. is hidden by default on Windows. See: Restore the Menu bar in Firefox
• Bookmarks menu button for the toolbar () - you can add this using the Customize panel. See: Customize Firefox controls, buttons and toolbars

Are any of those the thing you're missing?

To change your Firefox home page setting, see: How to set the home page.