I am not from the AccessShop Themes team, but seeing this question I wanted to share what I know.
The above question is out of the support area, maybe they can provide you a solution if you use the Request Customization option.
The solution to your question can be found on various topics on StackExchange for Magento. Also, this is quite a tricky and critical thing to modify the order/invoice number sequence or pattern. You have to make changes in database tables, not only one table a couple of them. A Magento expert can offer you best solution. And, there are a few extensions (mostly paid) available in Magento Connect.