ShopTab supports data files in CSV, XML and Google Product Search (text, tab-delimited) formats. Details on these formats and their implementation are available in our support database. You have two options when working with Magento.
1) You can export a file from the database in a CSV format and then manipulate it into the format needed by ShopTab.
2) Use a file exporter tool. We've had clients use Aten Software's free option - http://www.atensoftware.com/p186.php. This option provides a Google Product Search format which can be used directly with ShopTab in the DataFeed section of the admin portion of the website. It will also provide a CSV export option.