I have a WD MyCloudMirror and I have succesfully saved output to it from both my IP2M and IP3M-841's. I have used FTP in the past but found that it was more problematic (I kept getting video with the first few seconds missing) than direct connection using the NAS option which is supported by my NAS using NFS (network file system). I came to the conclusion, rightly or wrongly, that it was caused by the initial login using FTP. I have to be honest and say that I didn't put much effort into solving it because the NFS option works so well.
Can you make a note of the error message that you are receiving and post it here, that might tell us where the problem lies. It would also be a good idea to post the firmware version that is installed on your camera.
Edit: I've just had a go at connecting my cameras to my NAS via FTP and failed initially
I don't understand the bit about an error message in broken English. I initially got "Connection failed" and when I got the sequence right "FTP server test success".