Since you have a version of Pages that will not work on iOS 15.8.2, and there is no currently installable version of Pages available for iOS 15.8.2, then that leaves you with the Pages documents on your iPhone 6s local filesystem.
You can do nothing with them until in Settings, you tap your user name, click on iCloud and switch on iCloud Drive. Then the Files application will see iCloud Drive and you can then move your Pages documents to iCloud Drive.
Once the Pages documents are on iCloud Drive, you can access them from any Mac and copy them to a USB stick on a Mac or Windows computer for backup, and by using a current web browser you can also sign into Apple's iCloud dot com website and use Pages for iCloud on those documents. Even download them as Word or PDF documents.