You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'ORDER BY a.Price DESC' at line 2
Query
SELECT c.storeName, c.State, c.City, a.adID, a.Price, a.pictureName, a.Delivery, a.Shipping, a.Description
FROM customerInfo c inner join adInfo a ON c.customerID = a.customerID WHERE c.customerID=1428 AND ORDER BY a.Price DESC