Hello Peggy, Thanks for your interest.
On the App Store 'Purchased Page' there seem to be two things I can do regarding Pages, and the same two for Numbers. In a column on the right, some previously purchased apps have a button labeled 'DOWNLOAD', and some have a button labeled 'INSTALL'. But for Pages and Numbers the button is labeled 'OPEN'. When I press either, it causes the existing, older version, already installed on the computer, to open. Specifically, in the case of Pages, version 4.3. I'm supposing that the version I use on my iMac, 5.6.2 which I upgraded to when I upgraded the OS on that machine to El Capitan, would be more appropriate.
The other choice is that one can click on the name 'Pages', or its icon. Then I'm taken to a page describing the newest version, 6.0, which requires the Sierra OS. On that page there is an 'Update' button. When pressed, this causes a small wheel to spin near the left edge of the window's grey title bar, apparently indefinitely. The same thing happens with Numbers. This may be just as well, since these windows only seems to deal with version 6.0 (or 4.0 for numbers), and give no hint of a way to access other versions.
So, still stuck, any other idea how to move forward? Thanks