The dread “memory card not formatted” error message generally indicates memory card problems. This can occur for many different reasons including a virus infection, memory card problem, power surge, or problems with the operating system, etc. If you receive this type of error message, it is important that you act carefully to keep your important data safe.
1. Do NOT click "yes" to format the memory card in case that the formatting process makes things worse.
2. Do NOT attempt to write anything new on this memory card in case of any data loss.
3. Download a memory card data recovery freeware to help you:
In fact, this data recovery freeware was found as the camera memory card of my friend was mistakenly formatted. All his stored photos were also gone at the same time. But, this freeware finally restored all his wanted photos back completely. So, I believe it will also help you out.
So, try to read more detailed information of this data recovery freeware here:
4. Save and back up all your restored data on a different memory card or drive in case of data recovery failure.