If you don't have mount.nfs, then you don't have the nfs client package installed. That is probably the cause of your problem.
sudo dmesg | tail
FAT: Filesystem panic (dev mmcblk0p1)
The above device is for sd cards and not usb pen drives. Do you have an MMC sdcard reader? Anyway it has nothing to do with nfs.
The _netdev option goes in the forth column of your /etc/fstab entry for the share . If there is more than one option, you separate them with commas. There are probably examples in your current /etc/fstab file. If you mount the drive manually, then the options come after the -o argument, are are comma separated as well.
For NFS, the uid & gid numbers need to match for each user. Otherwise you need to allow everyone access by the "o" others permission bit. You may need to set this up in your nas interface, adding users and their UID numbers. Also check the nas documentation. We have been assuming nfs 3 but it may use NFS 4.