You can check the IBAN number for your account at TDB as well as other commercial banks through the following channels
TDB Online: Log in to your account, go to Transactions -> IBAN Inquiry, enter your account number, select the corresponding bank, and search to view the IBAN number.
TDB Website: Visit the bank's page at https://www.tdbm.mn/mn and navigate to https://www.tdbm.mn/mn/iban-lavlagaa, enter your account number, and click the "Inquire" button to find the IBAN number.