You're looking for a way to download Windows 10 IoT 2016 LTSB. Here's what I found:

Windows 10 IoT 2016 LTSB (Long-Term Servicing Branch) is a version of Windows 10 designed for Internet of Things (IoT) devices, such as industrial automation, retail, and other specialized devices. It's a stripped-down version of Windows 10, focused on device-specific functionality and security.