Imam
To be honest I have no clue what Klarna is asking and how it works exactly to pair it to your account. I'm very sure though that bunq doesn't have a clearing number and this is not something European SEPA banks generally have, unlike UK/SE banks on their national payment systems.
SEPA banks in Europe have IBAN's which contain all necessary information. In some cases services ask for the BIC/SWIFT (BUNQNL2AXXX) additionally, but this information should/could be pulled from the IBAN.