I want install Pages macOS monterey

If your Mac came with Pages pre-installed by Apple or a third-party reseller, then you cannot get Pages v13.1 for Monterey. You can get this last compatible version of Pages for Monterey provided that you have previously installed Pages from the Mac App Store since Oct 2013.

If you did… then launch the Mac App Store and sign in with the same Apple ID that you previously used to install Pages from the Mac App Store. Then press cmd+0 (zero) to open the Purchases page. There should be some download indicator next to Pages on that screen and you should click that item. One or more dialogs may appear, none of which you will click Cancel, and the last one should offer to install the last compatible version of Pages for macOS Monterey.

Unless you had Pages in a Previous OS, for some reason Apple doesn;t allow you to get a newcopy for an old OS.

Do you actually need Pages, or just a good Page Layout App?

Look into the Free LibreOffice, it handles MS Office files like Word & Excel, & Page Layout…

https://www.libreoffice.org/