If you saved your designs when you placed your order, you will find your backup in your personal space, saved designs tab > ordered designs tab.
You will then be able to consult, modify and re-order your saved designs.
If this is not the case, you will find the "Re-order" button in your order details, under the "Orders" tab. A request will then be made to generate a new order using the same print file as your initial order.