How do I search for an old photo in my image library?

I am looking for an old photo we used a while back in our newsletter. How can I search for that photo? 

Thanks! Also, today, everytime I try to download a jpeg for use on the newsletter, it turns into a jfif. And Constant Comment won't accept a jfif ext. Or if it will I need someone to eplain to me how!

Thanks!