How to force sql server to use mixed mode authentication in Powershell

$instanceName = get-itemproperty ‘HKLM:SoftwaremicrosoftMicrosoft SQL ServerInstance NamesSQL’ -name MSSQLSERVER

if ($?) {
$i = $instanceName.MSSQLSERVER

set-itemproperty “HKLM:SoftwaremicrosoftMicrosoft SQL Server$iMSSQLServer” -name LoginMode -value 2 -type dword
}