getting a 43 message, what do i do, previously got a 36 error code

I am trying to download photographic images that are very important to me, from a sandisk sdhc 16gb card, used in a canon 6D full frame digital slr...what can i do to access or recover the images? how do i know if they are on the card? i am using a macbook with 10.6.8 operating system, thanks, virginia