Converting Access Databases to Apple Numbers
First, a word of caution: If you work with a large database, this might not be the right application to use. Apple Numbers usually freezes, crashes or displays error messages when trying to open documents that contain more than a few thousand rows, no matter what format. If you have a small database, you have several options for getting your data from the Access database into Numbers:
Apple Numbers supports opening Excel documents. Saving your database as an XLS file is the recommended way for converting Access databases to Numbers. See the page about Converting Access Databases to Microsoft Excel for more details.
Copy & Paste
Quite simple: Select the rows you need (or select all using ⌘A), then copy and paste them to Numbers.
Numbers '08 always expects the International CSV format. In Numbers '09, the format depends on your region setting in System Preferences.
Numbers automatically detects if you use the UTF-8 or MacRoman encoding. UTF-8 is recommended when your data contains characters from foreign scripts.
For more details on CSV see the section on Exporting Access databases to CSV.