Use this Media Creation Tool :
You have 3 options :
1.) Click the Update now button.
That will bring out the Upgrade Assistant to check if your machine is ready for CU. If approved, just follow the prompts for download/installation.
2.) Click the Download tool now button.
Select Yes to confirm.
Select Create Installation media for another PC.
Select the same Language, Edition and Bit-version your Win 10 is currently using.
Select ISO File option.
That will begin downloading the iso to your computer.
When download is completed, Right click at the iso file > click Mount > click Setup (or setup.exe).
Installation will begin.
No product key is required.
You can keep your files, settings and apps.
Activation is automatic.
3.) Burn the iso file to a bootable media (DVD or USB) > use it to do a Clean Install.