Microsoft has ended support for macOS Monterey (12.*) as they only support the current release of macOS and the previous two releases (Sonoma 14.*, Ventura 13.*, Monterey 12.*).
You may be able to upgrade your Mac to Monterey per macOS Monterey is compatible with these computers - Apple Support
and obtain the full Monterey installer from the Mac App Store via How to download and install macOS - Apple Support as only Sonoma is directly available in the store now.
If you want Microsoft document compatibility in an Office clone that avoids this Microsoft merry-go-round, consider looking at the free trial of Softmaker's Office NX, or 2024 for Mac, which at present, supports macOS Catalina (10.15.*) and later.