This starts with R followed by 10 or 11 numbers. ie R2020123456. You can find it in the confirmation email you received after booking. If you booked with another company, please contact them directly as we will not be able to help you.
NOTE: if you booked via the Railplanner App, please check if it was with our own platform (Book with Interrail/Eurail) or another one (e.g.: Book with Deutsche Bahn).
A member of our support staff will respond as soon as possible.