Migrating AD from Windows Server 2003 to Server Essentials 2016
Is there any documentation for migrating a Windows 2003 Standard AD to Windows 2016 Essentials?
Worth noting is that Windows Server 2019 Essentials is 'just-around-the-corner' and you might want to wait until that newer version is generally available.
Here's one for standard server to 2012 essentials. The steps for 2016 essentials would be the same.