After adding the column, right click on the OU and export list to CSV. Open the export file in Excel and that should display four columns A through D in column E2 (row 1 is header) paste powershell script from below. Replacing Domain, Policy Name and OU (add more to the path if users are deeper then one OU)
=CONCATENATE("DOMAIN/OU/",A2,"' | Enable-UMMailbox -PinExpired $false -UMMailboxPolicy 'Policy NAME' -Extensions '",D2,"'")
Now drag using the copy square to the bottom. Now that column E has all of your scripts to enable all those users you can copy and paste them into your Exchange enabled powershell window. The safer method could be paste into a powershell script. Pretty simple little method to get all your users up with Voicemail. By the way this does send out emails with their new Voicemail PIN.