Do you have an external SD card reader that you can plug into another device? If the card is bad, you will lose everything on the card. If it's just seated improperly, simply taking it out and reseating it should do the trick. If it's not showing your photos in the Gallery, it's because you used the SD card as the default photo saving location, and if the card is not readable, it will not see the photos. Open Google Photos, your photos should have been backing up to Google. If your photos are showing there, you can just download them to a new SD card when you get one (assuming the card you have is faulty).
