Try this:
$before = "01/29/2010 9:32:22.196 168 99.99999234234 99.34234324234234 95.23123324234324 47.321999230984"
$regex = '(?< date >\d{1,2}/\d{1,2}/\d{1,4})\s(?< time >
if ($before -match $regex)
{
$after = $Matches["date"] + ' ' + $Matches["time"] + ' ' + ($Matches["someData"] -replace '\.', ',')
}
$after