If you installed Pages from the Mac App Store since Oct 2013, then it is possible to obtain the last compatible version (13.1) of Pages for Monterey 12.7.6. Otherwise, your option may be Peggy's response in Pages app, and the lack of ability to dow… - Apple Community or using Pages for iCloud. Like Peggy, I have not tested that approach.
The last version of macOS to support Pages '09 was macOS Mojave 10.14.6.
If you did install Pages v5 or later per the first paragraph, then launch the Mac App Store in macOS Monterey, and sign in with the same Apple ID you used to install Pages previously. Then press cmd+0 (zero) to open the Purchased panel. Pages would appear there with the means to download the last compatible version for Monterey. You may see one or more dialogs and do not click Cancel on either.
Understand that Apple did not base Pages v5 (10/2013) or later on Pages '09 features or functionality, so you will be dealing with a different application in Pages v13.1. The document architecture also changed so you cannot just open Pages v5 or later documents in Pages '09. I would strongly recommend that you back up all of your Pages '09 documents and only open copies of them in the newer Pages applications as the documents will get converted to the new document standard. Same is true for all other current Pages implementations on iCloud, iOS, and iPadOS. There is a means to export to Pages '09 format, but stripping out features unique to the current Pages application.