You can get your copy of MDT 8450 from the Microsoft Download Center.
This update supports the new Windows Assessment and Deployment Kit (ADK) for the latest version of Windows 10, version 1709. Several bugs were fixed in this build. Check out the blog listed below for the details and an FAQ!
Ref: “MDT 8450 Now Available” - https://blogs.technet.microsoft.com/msdeployment/2017/12/21/mdt-8450-now-available/