Here's a quick Powershell one-liner to list all the Organizational Units, or OUs, in your Active Directory domain. Firstly you'll probably need to load the ActiveDirectory module. This can be done at the Powershell prompt with the below command;

Import-Module ActiveDirectory;

Then we can use the Get-ADOrganizationalUnit cmdlet to retrieve a list of OUs.

Get-ADOrganizationalUnit -Filter * | Select-Object -Property Name | Format-Table -AutoSize;

This will display a list looking something like below;

Domain Controllers Microsoft Exchange Security Groups Security Groups Domain Servers Domain Workstations Domain Guest Accounts Printers Management Virtual Desktops IT Service Accounts Users Computers Production Servers SQL Servers Web Servers