There is no upgrade path from Windows 11 Enterprise to Windows 11 N Enterprise.
These are upgrade paths from Windows 11:
Windows 11 Pro N edition > Windows 11 Enterprise N edition.
Windows 11 Cloud N edition > Windows 11 Enterprise N edition.
Windows 11 Core N edition > Windows 11 Enterprise N edition.
If you have Office 365 licensing that includes enterprise, the pro license will be upgraded to Windows 11 enterprise.