Zend certified PHP/Magento developer

Unable to upgrade sercomm rv6699 using MobaXterm

I am trying to update software of sercomm rv6699 gpon terminal using tutorial from the web.

Tutorial says following (original is here):

  1. Put software files (called mtd12, mtd1, mtd0) on USB flash drive, formatted as fat32;
  2. Connect to your router by SSH using MobaXterm;
  3. traceroute ; /bin/sh
  4. mkdir /tmp/sdb && mount /dev/sdb1 /tmp/sdb && cd /tmp/sdb
  5. mount
  6. dd if=mtd12 of=/dev/mtdblock12 && dd if=mtd1 of=/dev/mtdblock1 && dd if=mtd0 of=/dev/mtdblock0

I connected to router using SSH and ran command as said:
enter image description here
After that I opened terminal and ran 3.:

enter image description here

And got an error:

mount: /tmp/sdb: Invaid argument

How this problem can be resolved?