We are planning to upgrade our ArcGIS Server and Portal for ArcGIS 10.3.1 installation to Enterprise 10.5.1 and use a new VM with Windows Server 2016. I'm thinking of using the Enterprise Builder tool to create the site, since it's supposed to make the 10.6.1 upgrade easier. Is there a way to copy the existing Portal configuration to the new 10.5.1 Portal? Also, can I use ArcGIS Online Assistant to copy the content from 10.3.1 to 10.5.1? As a side note, we aren't upgrading to 10.6.1 quite yet because we will also have to upgrade ArcFM to 10.6.1, so that project will happen next year.