Windows 2016 Evalutation Edition to Standard

Hi,
An evaluation version can only be activated using a retail key, if the key was from volume center then you'll need to use volume distribution media that can be downloaded from volume licensing center.

https://www.microsoft.com/Licensing/servicecenter/default.aspx

And I recommend for you test in UAT or DEV environment first. After will to activate on production is more safe.

thanks, I hope you and all of your family are fine in this COVID-19 period. Also sorry for weakness in my English.