A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
There is no Backstage in the Mac products. That is a contrivance of the Windows products.
Some - but not all - accessed via the Win Office Backstage can be found in the File menu on the main menu bar. Other items are located elsewhere or are not available on a Mac. If you'd specify what you're looking for someone can guide you to the right location if it exists in the Mac product.