You specify the filesystem type with the -t
option. As described in man mount
:
-t, --types fstype
The argument following the -t is used to indicate the filesystem
type. The filesystem types which are currently supported depend
on the running kernel. See /proc/filesystems and /lib/mod‐
ules/$(uname -r)/kernel/fs for a complete list of the filesys‐
tems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat,
sysfs, proc, nfs and cifs.
So, to mount a FAT32 (vfat) drive, you would run:
sudo mount -t vfat /dev/sdc /media/usb
However, you don't mount devices, you mount partitions. What you're after is probably:
sudo mount /dev/sdc1 /media/usb
Or, if it still complains:
sudo mount -t vfat /dev/sdc1 /media/usb
For more details, update your question with the output of sudo fdisk -l /dev/sdc
.