OK with that information I downloaded the manual for your camera and section 4.4.8 FTP gives all the information you need assuming that you have setup the NAS FTP server correctly.
NAS FTP.
Log in to the nas web UI.
Go to 'Management' --> 'Application Management'
Select FTP and fill in as necessary.
Then SAVE.
Next go back to 'Management' and select 'Account Management'
Select 'Network Shares'
Make sure you have the required share name and have selected FTP for that share.
log out of the NAS.
Now test to see if you have the nas FTP server up and running by downloading FileZilla and installing it.
Open FileZilla and fill in the IP address of your NAS, then the user name and password (the port can be left blank if it is 21), then click connect.
This should bring up the shate on the nas in the right hand section of the display.
If there are any problems read the connection log - top section.
IF you were able to login to the nas share with FileZilla you then use the same settings in the FTP dialogue on your camera - with the addition of changing 'FTP Mode' to PASV.
Click the test button and hopefully it will connect in which case you are up and running.
This assumes that they are both on the same network and subnet. There are no changes that need to be made to the router because it is only acting as a switch and passing the data between the camera and nas. The nas is the FTP server with the camera being the FTP client.
The only other thing I should say is that both the NAS and camera should have fixed IP addresses as this simplifies working together.
BTW, when you mention CuteFTP is that an addon or the one built into the nas (all of our nas boxes announce themselves as PureFTP)?