Once you've downloaded the Windows 10 version 1607 ISO file:
Go to the tab (found under "More tools" if not visible).
Downloading the Windows 10 version 1607 ISO file requires careful attention to ensure that you obtain the correct edition, language, and architecture. This report provides a step-by-step guide to downloading the ISO file using the Media Creation Tool and direct download links.
This popular bootable USB creator includes a "Download" script that allows you to select "Windows 10" and then pick "Build 14393 - 1607" from a dropdown. It downloads the file directly from microsoft.com .
The server equivalent of version 1607 is still available for evaluation via the Microsoft Evaluation Center Trusted Third-Party Alternatives
is technically legal if you own a valid Windows 10 license. However, Microsoft strongly discourages running outdated versions.
You can use this page to download a disc image (ISO file) that can be used to install or reinstall Windows 10. How can I stay on Windows 10 1607? - Microsoft Q&A