The last version of Pages available:
macOS 10.15.7: v11.1
macOS 11.7.10: v12.1
macOS 12.7.4: v13.1
macOS 13.6.6: v14.0
macOS 14.4.1: v14.0
The current Pages v14.0 in the Mac App Store requires macOS Ventura (13) or later. If you are on an older version of macOS, then you cannot get this version. If you previously installed Pages yourself using your Apple ID, then you can get the latest version for your operating system — unless Pages was pre-installed by either Apple or an Apple reseller.
If you are on the two operating systems supported by Pages v14.0, then you can download it from the Mac App Store. For older operating systems, launch the Mac App Store and sign in with the same Apple ID that you previously used to install Pages. Press cmd+0 (zero) to open the Purchased panel and locate Pages. Click the download/update button and do not click Cancel on any dialog that appears. The last (perhaps only) dialog will ask you if you want to install the last compatible version of Pages for your operating system. Do that.
Because you have Pages v11.1, if the preceding paragraph fails for some reason, it may be that older version of Pages that is installed. With it backed up, remove Pages v11.1 and then repeat the preceding paragraph.