Pages and Numbers for Big Sur

If you installed Pages or Numbers on macOS since Oct 2013, then you may be able to get v11.1 of Pages and Numbers for Big Sur. If you didn't install these applications, and they came preinstalled, you cannot get them now from any source.

If the first sentence above is true, launch the Mac App Store and sign in with the same Apple ID as you used previously. Press cmd+0 (zero) to open the Purchase panel and if these applications are present, click on the blue download symbol. You may receive one or more dialogs that you do not click Cancel. The last one will offer to install the last compatible version of the application for macOS Big Sur.