You can run it from any DC, really, but I prefer to run it from the destination server for them. You can utilize what you want out of it, but this will also try to increase the domain/forest functional levels to the most recent, as part of the process. I also don't have the logic yet to query OS versions of the DC before running the functional role increase, so you'll want to confirm that all DCs are at least Server 2016 before running the entire thing. Perhaps I'll work the logic in next week to check before running that part.

$FSMORoles = Read-Host "What is the destination server for FSMO roles?"

<#
Roles
0 - PDC Emulator
1 - RID Master
2 - Infrastructure Master
3 - Schema Master
4 - Domain Naming Master
#>

#Migrates the FSMO roles to server defined in $FSMORoles
Move-ADDirectoryServerOperationMasterRole -Identity $FSMOroles -OperationMasterRole 0,1,2,3,4


$addomain = Get-ADDomain

#Extracts information from get-addomain output to use in the domain functional level upgrade
$domainmode = $addomain.domainmode
$domaindigit = $addomain.domainmode.value__
$domainname = $addomain.DNSRoot

$adforest = Get-ADForest

#Extracts information from get-adforest output to use in the forest functional level upgrade
$forestmode = $adforest.forestmode
$forestdigit = $adforest.ForestMode.value__
$forestname = $adforest.Name

Write-Host -ForegroundColor Cyan "Current Domain/Forest Mode: $domainmode/$forestmode"

#Increases domain functional level to the highest possible
if ($domaindigit -lt 7) {
    Write-Host "Increasing Domain Functional Level..."
    Set-ADDomainMode -Identity $domainname -DomainMode 7
} else {
    Write-Host "Domain Functional Level is already at the target level (2016)."
}

#Inreases forest functional level to the highest possible.
if ($forestdigit -lt 7) {
    Write-Host "Increasing Forest Functional Level..."
    Set-ADForestMode -Identity $forestname -ForestMode 7
} else {
    Write-Host "Forest Functional Level is already at the target level (2016)."
}
#Output for all above changes in a view to confirm changes
$domaininformation = Get-ADDomainController | ForEach-Object {
[PSCustomObject]@{
    ServerName= $_.Name
    OperationMasterRoles = ($_.OperationMasterRoles -join ', ')
    DomainFunctionalLevel = $addomain.DomainMode
    ForestFunctionalLevel = $adforest.ForestMode
    }
}

$domaininformation | Out-GridView