Older IOS system

The version of Pages that the App Store offers requires macOS 12.3 (Monterey) or later. I don't think there is a way to get an earlier version of Pages from the App Store if you've never had it before.

iWork '06, '08, and '09 shipped on CD-ROM or DVD-ROM discs, so you may be able to find used original copies of those. iWork '09 will run on Mac OS X 10.5.6 or later.

iWork: System Requirements

It would help to include which macOS version (and it is macOS, not iOS, with a computer).

If you have access to a newer computer, download the app using your Apple ID on the new computer. Then go to the old computer (or a mobile device signed into your ID) and see if it then offers to let you download the app on that.

I know a couple of years ago I was able to download Mavericks version Numbers, Pages, and Garageband once I had downloaded them on a computer running Mojave. It would be nice to know definitively from somebody who has actually tried doing this recently if this is no longer possible.

Do you needPages or would a similar App work?

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

https://www.libreoffice.org/

You may wish to read the posts in this thread: How can I get Garage Band for OS 10.14? - Apple Community

I have no idea what it means, but in 10.13.6 it says I can Update under purchases...

And in Mojave it just says I can Open them under purchases...