Grep Multiple files with powershell

Hi there,

The follow produce output with grep: Could not open 'ROVER0151.html ROVER0153.html ROVER0161.html ROVER0163.htm
l ROVER0165.html ROVER0171.html ROVER0173.html'

$file = "ROVER0151.html ROVER0153.html ROVER0161.html ROVER0163.html ROVER0165.html ROVER0171.html ROVER0173.html"
echo $file
grep -ri 'Enforce password history' $file