Order settings
Controls how orders are numbered and how long an unpaid order is held before it expires.
Settings
Order Number Prefix - a prefix added to the front of every order number. This is useful for telling orders apart when you run more than one store, or for matching the store's numbering to your own accounting system.
Expiry Time In Hours - how long an order is held before it expires. This governs how long stock stays committed to an order that has not been paid for.
How to Update Your Order Settings
Select the store you would like to update
Click on Manage Store Settings underneath Settings
Open Orders
Open the Order settings section
Set the order number prefix and expiry time
Save your changes
Changing the order number prefix affects new orders only. Orders already placed keep the number they were given.