How to reinstall DO12 when Win10 is replaced and C-drive reformatted

My Windows 10 Education installation is very sick, and is not fixable. Thus, I am forced to purchase another version of Win 10 Home, reformat my C-Drive, install the new version of Win10, and then reinstall all applications.

I currently have Opus 12 Pro Edition installed on the C-drive. What must I do to ensure that I will be able to reinstall it when the time comes?

I have no recollection as to whether I formally registered with DO when I installed an earlier version.

Please advise.

You don't need to do anything special. Just install it the same way you did the first time.