ADMT stands for Active Directory Migration Tool and is used to migrate AD objects (such as users, groups, computers, etc.) from one AD forest or domain to another, supporting complex scenarios in the process.

Why Microsoft hides their most useful tools is a mystery though. So here are the download links. You will need to accept some EULAs and have a Microsoft Account if you wish to download it though.

1. Navigate to https://connect.microsoft.com/site1164/program8540.
2. If you have not done so, you will have to log on with a Microsoft Account and join the program and accept its EULA things.
3. Then, you will be able to click through to the download page and download ADMT version 3.2, and, if required, PES v3.2.

UPDATE 2017-01-19:

The download links work again, and, because it's not allowed to distribute the packages, I've taken down the mirror link.