I can't take pictures it's showing Format error

It can possibly be four different factors:

1. Your SD card is formatted in a format that differs from the one that your camera is able to use. In this case you'll only need to format it to FAT32 on your PC (you can find plenty tutorial on this website or on YouTube).
2. Your SD card has an architecture impossible to read by your camera. Check that your camera supports the type of SD you're using (may it be SDHC, SDXC or others)
3. Your SD card became corrupt and the camera isn't able to read or write to it because of this. If this is the case you'll need to buy a brand new SD card;
4. Your camera has a faulty memory reader unit, or worse, your camera could have a faulty CPU. If none of the things I've listed before is the problem, you shall buy a new camera.