You can verify and download this version directly from the Apple Support website. It is usually bundled within a specific model's support package, but direct download links are often found on software archive sites or via the Apple Boot Camp Support Software page.
Why does that matter? Because 7866 corresponds to a tied to Windows 10 version 1903 (May 2019 Update). It included:
It is important to note that "downloading Boot Camp" usually refers to downloading the (drivers) from within macOS to be installed onto a USB drive or the Windows partition.
