|Place it back into your phone, does it still have your data? Definitely do not format!|
If it does, the file structure on the SD Card is likely not readable PC format and that's why your computer wants to format it. Plug your phone into your PC to transfer whatever you want off the SD Card to your PC
If it doesn't show your data on the phone anymore, then you are going to want to do a RAW recovery on your SD Card with a program like GetDataback.. I had this happen with a camera SD card one time, putting the card into another camera corrupted it and I had to do a raw recovery to get the pictures back.
Thanks for any input.