Microsoft does not sell single licenses of IoT Enterprise LTSB 2016 to the general public. You would need a subscription like Visual Studio Enterprise (which includes Azure Dev Tools for Teaching, formerly Imagine) – but even that typically provides newer LTSC versions.
After October 2026, using LTSB 2016 on any internet-connected device becomes a major security risk. New vulnerabilities will remain unpatched. windows 10 iot enterprise ltsb 2016 iso download