OK, you missed some of the net use command
[left out drive letter to attach network storage to]
1> Net use X: \\server DNS or IP\Network.Share\to\connect\to\specified\drive\letter /user:serverDNS*(note 1)\username password*(note2)
2> Robocopy X: [or specified drive letter]\*.* C:\location\of\backup\directory [don't forget to create directory with mkdir beforehand
3> net use X: /del /y [disconnects share without confirmation question]
(note 1) use ip if needed but that can get hairy here usually needs either Winbind name or DNS which ARE DIFFERENT google enable winbind ubuntu (or your flavor of Linux) it is super easy to do most of the time. I have used either the FQDN as well as the winbind name interchangeably but IP in user part of command almost always fails.
(note 2): For security leave password off your script would stop and ask you for password after it runs the net use command and it connects and then once you enter it and hit the enter key it will continue with script. This does not have you leaving your password in a plaintext script file for more security, but sometimes you need to have script not stop
[ie logon scripts]
Also I think you may be going about this odd ways [it works just requires more settings and effort than a VPN]. If it was me from a windows client to a *nix host I would recommend a using a VPN server like OpenVPN then you could use the bridged setup and become just another client on the network [with SSH you are connected to the server directly and would need to setup port forwarding through SSH to get services to pass through to your physical client directly], but forget that for a minute you don't seem to have net use running correctly, so if that works then read on and using your current setup should work
Net use is for setting a drive letter try:
NET USE X: [OR ANY DRIVE LETTER NOT USED] \\192.168.10.90\home\lgr /user:server[username] [password]
you can run net use in all lower if you wish Windows does not care about case like Linux or Unix or Mac OS X btw
BUT BE WARNED YOU DO NOT WANT TO MESS WITH IPC$ IT IS HIDDEN FOR A GOOD REASON IT HANDLES ALL COMMUNICATIONS BETWEEN ALL APPLICATIONS ON A WINDOWS MACHINE [AND ALL NETWORK TRANSACTIONS] BACK IN THE DAYS OF NT 4 I GOT BORED AND DELETED IPC$ SHARES OF PEOPLE WHO ANNOYED ME WHY? YOU LOSE ALL AND I MEAN ALL NETWORK COMMUNICATIONS PERIOD [NOT TO MENTION ANYTHING LIKE CLIPBOARD ACCESS BETWEEN PROGRAMS. TO GET AN IDEA OF HOW INTEGRAL IT IS SEE: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365574(v=vs.85).aspx YOU NEVER NEED TO CONNECT TO IPC$ SEE BELOW IN NET USE YOU SPECIFY A DRIVE LETTER AND IT AUTOMAGICALLY CHECKS WITH IPC$ TO ENSURE YOUR CREDENTIALS ARE VALID. I REPEAT I WARNED YOU ABOUT IPC$ DO NOT MUCK WITH IT UNLESS YOU KNOW WHAT YOU ARE DOING AND REALLY MUST TOUCH IT.
OK so after warning:
NET USE X: [OR ANY DRIVE LETTER NOT USED] \\192.168.10.90\home\lgr /user:server[username] [password] [note we are using CIFS [SAMBA so directories are referenced as you would in Winblows]]
Robocopy X:\File.ext [or pattern like *.txt] C:\some\directory\to\save\to\file.ext
Net Use is Net use drive letter for network location in plain english really so don't forget to actually specify the drive letter [without drive letter it does kinda test the connection, but doesn't tell you you really are not using net use correctly].
Then we use robocopy to copy from the now in use drive letter which now points to a network location we told it to and copy from there to local [OR another net location should you use net use to map a second net location to a 2nd drive letter :-O ].
and when all done to disconnect
net use x: /del /y [net use on x: delete yes delete without asking me]
net use * /del /y would kill ALL connected net shares
and just net use in windows would list connections you have open and while it will connect to just a computer name that is just more of a direct confirmed peer-to-peer but still network based connection. The point behind net use is to take \\a really\long\network\share path and assign it to a drive letter so \my.server\net\share\somewhere becomes just X:\ [or whatever is free between A: and Z [I would not use A: B: C: D:] these are reserved A and B for floppies C: Main drive windows loads from and D: is normally CD/DVD drives [this is not hard and fast it can be different but generally this is how it goes] so I recommend lower in the alphabet letters like L - Z but totally up to you.