Overdrive e-book & audio book App

iOS and iPadOS
Dear All, I downloaded the Overdrive App a couple of weeks ago and it's great. However, does anyone know how to switch from the e-book search to audio book search? I can't work out how to do it. However, if all books in search are listed and you haveto choose between e-books and audio books, does someone know how to do this? Many tanks, Steve.