Bulk Convert to IBAN. Convert massively your Piraeus Bank accounts to IBAN. First, you must select the file type. Afterwards select the file that you have stored your 13 digits account numbers in one column only and fill in the Verification Code appearing on the screen. At last, type your email address to receive the processed file and click the "Bulk Convert to IBAN" button. Permitted file types: * .txt, * .csv.