You can view the details of your client's order by heading to the main menu and clicking Selling » Orders.
When you first visit the order screen you will see a list of your currently open ("new" or "ordered") orders. To view previously fulfilled or canceled orders, or to simply filter the open orders by name or order number, click the box next to "Showing Data For:" and change the filter/search details. Once you've selected the filters of your choice, click Apply to view the filtered results.
A date-range filter has been added to the Selling » Client Orders page. Once an account has more than a couple dozen orders on it, it can be fairly tricky to find an order if you don't remember the person's name or their email address. The date-range filter helps with that by allowing you to view a set of orders within a specific date-range, instead of simply viewing every order that you've ever received. You can also combine the date-range filter with the other filters, such as a person's first name ("Jane") and a date-range.