Remove the card immediately
When a camera shows a card error, stop shooting and switch the camera off before removing the card. Continuing to use the card can overwrite photos.
Do not format
Both the camera and the computer may offer to format the card. Do not accept. Formatting creates a new structure and can make recovery harder.
Safe checks
You may try the card once in a good card reader on a computer. If it asks to format, shows as RAW, or does not appear at all, stop and contact a professional.
Protect the card
Keep it in a case, away from heat and moisture. Do not bend a microSD card or try to clean its contacts aggressively.
Important: Switch the drive off if it makes unusual sounds. Stop using the drive immediately.