bookmarks disappeared

If the window is in the Full Screen Mode, press the esc button to exit Full Screen Mode.

Click "View" menu in the menu bar and choose "Customize Toolbar".

From the sheet that drops down, drag the default set into the Toolbar.

Click" View" menu i the menubar and choose "Show Favorites Bar".

For more info: Customize the Safari browser window on Mac - Apple Support

Do you have a backup you can restore from? If you have a Time Machine backup, open the Time Machine application, and go to a backup when you had the Bookmarks. Paste the below into the search box and restore the file.

~/Library/Safari/Bookmarks.plist

You are welcome.

Thank you!!!

You are welcome.