Not really sure what you are saying here, what do you mean you downloaded your iphone 10 from Windows 10? Do you mean you backed it up in iTunes? And you are trying to do what with an iphone 6 now? Restore it? But you said you did not back it up, or you did but there is no backup for it only for the 10? You may want to re-word your post a bit to clarify what you are trying to do and what you did.