I hope you haven't re used it since formatting. If you did that can make it more difficult. Here's the link to a good source for recovery software & I'd start with Recova which has a good reputation for doing it..
If you don't have any sucess with the free programs available Sandisk Rescue Pro can be downloaded for a test & if it finds the missing / damaged files you can then pay the licensing fee & retrieve your photos. I have used Rescue Pro more than once with excellent results. (Bailed out friends & relatives who either pulled the cable out while downloading or who formatted in camera by accident). Rescue Pro found files burried from more than 1 in camera format & reuse. Lexar also has a very good program for this but I don't remember it's name. .