jaredstuff

$terms = @()

#set terms
$terms = "Term1","Term2"

#set mm field
$mmfield = 'MM'

#get term info
$tg = Get-PnPTermGroup -Identity "Site Collection - drewmadelung.sharepoint.com"
$ts = Get-PnPTermSet -TermGroup $tg -Identity "TermSet"

$var = @{
    $mmfield = @()
}

#add terms to table
$terms.ForEach({
    $t = Get-PnPTerm -Identity $_ -TermGroup $tg -TermSet $ts
    foreach($key in $($var.keys)){
        if($key -eq $mmfield){
            $var[$key] += $t.Id.ToString()
        }
    }
})

#set item
Set-PnPListItem -List $list -Identity 4 -Values $var -SystemUpdate