Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Kay, you can only reinstall a retail version of Office 2013 from the Office Account at: https://account.microsoft.com/services you need to sign in with the same Microsoft Account used to install Office for the first time.
If you Office came preinstalled as a package from the computer company you may not be able to recover it. If you paid separately for your Office 2013 then it is a retail version.
PS: If you are only missing Excel>Type in the windows search box>Excel 2013>It should bring up the Excel App>Right click on it>Choose>Pin to start/Pin to taskbar.