You want to improve your English, and you're interested in audiobooks, and wondering where you can find them.
Actually, to make good use of audiobooks you need a high level of English. And they're expensive. What you might need is an audio course on CDs or mp3. A good bookstore should have them. If you're good at using computers, there's a lot of spoken English you can download. You could try Voice of America, BBC, CBC.ca (Canada). For courses, I hesitate to use usingenglish.com to endorse a commercial product, but I've found materials by Living Language to be very good.
wishing you success
peace be with you