Sales Pack Sheet report shows per-item sales quantity totals, by date range, optionally grouped by area.
Install WP e-Commerce Store Sales Pack Sheet either via the WordPress.org plugin directory, or by uploading the files to your server WP e-Commerce is required, installing this plugin without WP e-Commerce installed doesn;t make much sense and you will get an error message if the plugin can't fild the WP e-Commerce tables it reports on.