If it won't show up on any device, then the card won't be accessible to get anything off of it. And were you to do anything on it like format it, that would just erase what is on it.
If it isn't from either of those devices, and is from a different one, then you should put it back in the original device to see if it will still read it. If it does, then connect that device to the computer via USB (don't remove the card) and get the data that way.
NOTE: For future reference, it is better to leave a SD card in a device and connect the device to a computer to get the data, rather than removing the card and transferring the card to the other device. That leads to the card going bad.