As bhg481 states, if you've not got a program on your computer you need to go through the installation process to acquire it. For that, you need the setup files, rather than the program files from another drive.
However I'm wondering whether you've actually lost Microsoft Word anyway. It might be that the program is still there but the shortcut to it has disappeared. Try using the search box to look for 'Word'. If it's there, you'll simply need to add a shortcut to it onto your desktop, taskbar or apps menu.
Otherwise forget Microsoft Word and install OpenOffice instead:
https://www.openoffice.org/