If you just want to save the full path to a single instance of the file, you can use
$path = ls -recurse -filter "PsExec.exe" | select -first 1 | select -expand FullName
Or you can save multiple properties if you want
$file = ls -recurse -filter "PsExec.exe" | select -first 1 | select Name,FullName,Directory
$file.Name
$file.FullName
$file.Directory