Hi,
If there is no important data, try to reformat again using command prompt.
If it is still not working, I would recommend to re-partition the drive.
1.Right click on Computer
2.Select Manage>>Storage>Disk Management.
3.Find your drive. If it shows “Unallocated Space”, right click and select “New Simple Volume” and create a new partition.
Check this discussion : http://forums.sandisk.com/t5/Mobile-memory-professional-cards/How-to-repair-micro-sd-16gb-card-It-shows-31mb/td-p/186959
Incase you have important data in your MicroSD, still format the SD card and use a recovery software to retrieve them.
You can try Recuva which is free software. Since it is a free software it may not dig deep to recover files like others paid software.
https://recuva.en.softonic.com/download
I suggest you to purchase paid software only if the files are listed in preview option of trial version. Software that I have used and can recommend are:
http://www.recovermyfiles.com/ or https://www.remosoftware.com/sandisk-recovery
