Your SUN number is your unique booking reference and you can find it in your confirmation email along with other important details about your booking.
You can also find your MYB by heading over to the ‘My Bookings’ section of our website, or via the app. You will find the MYB number on your paperwork or when you click to "View and Manage Booking".
If you are referring to your flight reference please follow this link: Flight reference
You will find steps on how to find your flight reference and the other names it may be called with your airline.