Hi Joann,
It seems that Numbers 3 has "stolen" (converted) a Numbers 2 (Numbers '09) document.
I created and save a document in Numbers '09. I named it "Numbers '09 saved in Numbers 3" as a test.
I opened it in Numbers 3.5.3 and saved.
Now when I try to open it in Numbers '09, I get this message:
Be sure which version of Numbers is trying to open a document.
Your Applications folder contains Numbers 3. Drag the icon to your Dock.
A sub-folder named iWork '09 contains Numbers '09. Drag the icon to your Dock.
Numbers '09 (3 column graph) on the left.
Numbers 3 (four column graph) on the right.
See this User Tip:
Need newer version of Numbers to open file
Regards,
Ian.