Where can I find Online "Shop Order Number"?

I have a problem with my touch screen and online troubleshooting dos not provide valid information so I decided to sublit a request to Fairphone Support. I filled the form but I need a “Online Shop Order Number” that I should find on my invoice. Anyone has an idea ?

You should find it if you log in to your shop account under https://shop.fairphone.com/sales/order/history/

Thank you. I tried every numbers and the one starting with FP worked. They could have mentioned in the help field.