You can format the microSD inside the 10C by following these steps.
1. Enter the Camera Configuration menu by pressing and holding the Camera Button for 8 seconds until you hear the voice prompt, “Camera setup”.
2. Rotate the Jog Dial clockwise or counter-clockwise to cycle through the different options.
3. When you hear the voice prompt, "Format SD card", tap the Phone Button to remove all of the files on the microSD card inserted into the 10C.
4. Tap the Jog Dial once to exit the Camera Configuration menu.
When you use a new card for the first time, always format it before using the camera.