Microsoft typically provides separate installations for the Windows operating system and Microsoft Office applications. When you install Windows from an ISO file, you are installing the operating system itself, not Microsoft Office. You can also try to reinstall for Microsoft office for Mac (if you use it) and try again.
In the previous case, to install Microsoft Office, you would generally need a separate installation file or use the online installer provided by Microsoft. During the installation process, you would be prompted to enter your license key or sign in with a Microsoft account associated with a valid license.
Mod note: Removed 3rd-party link.