error in mounting drive on Ubuntu Mate terminal

I am trying to access files in the partition named "Envision" from the Ubuntu Mate terminal. The output of df -h is as follows Filesystem Size Used Avail Use% Mounted on udev 855M 0 855M 0% /dev tmpfs 175M 5.9M 169M 4% /run /dev/sda2 96G 28G 63G 31% / tmpfs 874M 1.6M 873M 1% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 874M 0 874M 0% /sys/fs/cgroup tmpfs 175M 40K 175M 1% /run/user/1000 /dev/sdb1 30G 28G 2.1G 93% /media/snow/SanDisk-32GB /dev/sda3 126G 115G 12G 91% /media/snow/Envision /dev/sda6 76G 63G 13G 84% /media/snow/Softwares When I try to mount hard disk partition named "Envision", using sudo mount /dev/sda3 I get the following output mount: can't find /dev/sda3 in /etc/fstab Am I missing out on something? Kindly help.