Step 1: You visit https://tb.rg-adguard.net/public.php
On this website, you can download Windows 10 all versions: 1809, 1903, 1909 and 2009.
Step 2: You select the Windows (Final), then you select the Windows 10 version which you want to download
Step 3: You click “Download“
You will see a link download Windows 10 iso free from Microsoft
Source: https://getproductkey.net/download-windows-10-iso-microsoft/
If you want to purchase Windows 10 Pro product key, you visit https://saleproductkey.com/ ($25/key).