Hello Richard,
My Name is Chander and I am Independent Advisor and a fellow Windows 10 user like you. I hope I can help you on your concern.
There is no Microsoft supported way to un-format your data. You may need to use any third party tool like Recuva or remo recover. You should be able to recover the data if the HDD sectors have not been re-written.
https://www.ccleaner.com/recuva
http://www.recoverformattedpartition.com/
Let me know if you have any questions or concerns.
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.