Nicole Lynn,
Version 2 of Numbers (iWork '09) does have Mail Merge. If your profile is correct, that's probably what you are using. The instructions for using the feature are in the Pages User Guide PDF.
If your profile is out of date and you are using iWork '13 apps, you're out of luck. But, you can always go back to Version 2 of Numbers and Version 4 of Pages.
Jerry