Okey what are the issues you have seems like your usb is okey. But if you are unsure.
Just tap on the red - button from the right side and ok it will delete that fat partition of that drive doing that will destroy your any files which maybe stored in the drive.
And then it will be a Unformated space and then just tap the + and format it with fat32 or exfat then seebif your problem solves or not.
#while formating if you want to use exfat on the format volume pop up select other and then next and then you will find exfat.