You don't need the fstab to mount a file system once, you can use the mount command for that. Only if you want the file system mounted at startup would you enter a line in the fstab. However, on the mount command, you need to specify more parameters. First you need to create a mount point, let's say:
sudo mkdir /mnt/nas
Now tell mount what to do. Specify the file system type (CIFS for Samba) with the -t flag:
sudo mount -t cifs //192.168.0.200/volume1 /mnt/nas
Notice position and number of the slashes. If this command is successful, the contents of your NAS are accessible under /mnt/nas.
Depending on the settings of the NAS you may need to specify other parameters, like username/password, but try this first. When that works, edit the fstab.
