Normally you will find the IBAN for your bank account when you login to your bank on the Internet.
Here is a link where you simply submit your bank account and it calculates the IBAN for you.
IBAN is an international standard for bank account numbers. IBAN consists of a country code, control numbers, bank code and the bank account number. The purpose with IBAN is to make payments more secure and convenient.
Read more about IBAN on Wikipedia