UNC paths seem to work just fine for me. What have you tried and what error messages do you get?
Anyway, Get-ChildItem is gonna need the path to begin with. Using the full local path could perhaps be an option. Like... "\\d1da1723\c$\This Directory\Stuff\prdload"
Or you could mount the share with "net use" before searching through the files.
"net use /?" for help on that.
$a=Get-ChildItem "\\d1dal723\prdload" -r | ? {$_.psiscontainer -eq $false} | ? {gc $_.pspath | select-string -pattern "err"}
Write-host "Files with error code ERROR : $a"