How to install Pages on macOS Sierra?

The current version of Pages v11.1 requires that you have macOS Catalina or later installed on your Mac. Apple does not provide full installers for past versions of Pages. The last version of Pages for macOS Sierra was v7.2.

If you have never installed Pages before, then your only option is to use Pages for iCloud, and Apple provides a user guide for that on the Pages support site. Or, if your Mac is sufficiently recent and can upgrade to Catalina or later, then upgrade your version of macOS per the hardware requirements outlined in How to get old versions of macOS.

If you had Pages installed on macOS Sierra at one time and removed it, you can restore it from a Time Machine backup right back into your /Applications folder. You may be able to update it to Pages v7.2 by launching the Mac App Store, signing in with your Apple ID, and then concurrently pressing the option key and the Purchases tab on the App Store application.

That will reveal your past purchases, and if Pages is present, it may have an update button. If so, click that. You will be notified in a dialog that you will need one of the operating systems from the first paragraph installed to get the current Pages, but it may also offer to update your outdated Pages application to v7.2.