First of all.....
IF you had Windows 10 installed, running and activated on your computer previously then you can reinstall it to a new drive whenever you want.
IF you don't have the installation media you can get it from here.
https://www.microsoft.com/en-us/software-download/techbench
Once you have the ISO, you can use ImgBurn to burn it to a DVD or Rufus to burn it to a USB ThumbDrive, either of which you can use to boot your computer to perform the installation.
Just make sure you install the correct version (the ISO contains both home and pro) matching your previous installation, language and bit version (32 or 64 bit).
Regarding you other question.....
You can't overwrite an OS exactly, that's sort of the object here.... getting you up and running on the computer, then to replace your "data" (docs, music, videos, email, pictures, favorites, etc., etc.,) from your rescued data source.
You'll need to re-install the Operating System and then re-install your programs.
I've managed to work a few miracles in similar circumstances once the Operating System was installed but it involved booting to Linux and then copying a lot of various folders as well as registry hives and that is pretty far outside the scope of what we can do in a support forum.