TA needs bank details to send refund. What’s IBAN for Wells Fargo???

Travelgenio UK is finally refunding my canceled booking after 1.5 years of receiving the refund from the airline but sent me the following email:

We would like to inform you that since the payment was made more than 1 year ago, we can only refund the amount corresponding to the booking by bank transfer.

In order to complete the refund of your tickets, please provide the following bank details:
- Account holder (full name, no initials allowed).
- Account holder’s address.
- Bank name.
- Complete bank address.
- Account number.
- IBAN.
- SWIFT or BIC.

My bank is Wells Fargo and they don’t have “IBAN”. I’m afraid if I leave anything missing, they’ll not process the transfer.

What to put for IBAN?