Download Windows 10 Anniversary Update?

I am getting a new iMac 2017 and want to install Boot Camp and Windows 10. From what I've read, I will need to install Windows 10 Anniversary Update and then upgrade to Creators Update. But I cannot find the Anniversary Update ISO anywhere on Microsoft's download site. Their own Boot Camp support doc page links to here...

<https://www.microsoft.com/en-us/software-download/windows10ISO>

...but the only edition avaiable is "Fall Creators Update". Is there somewhere else I need to go to get the older ISO?

Thanks!