Try using the IP address instead of the NETBIOS name, it’s usually more reliable that way. Also the error you are getting is because the /mn folder needs to be created beforehand (the mount command doesn’t create the mount point for you). Also make sure you have the cifs package installed for your distro. Hope this helps :)
It’s using the current user “root” as a login user for the share. You can specify a different share user using following command:
Try specifying a user that does exist on your Windows machine. Not quite sure if it will work without a password, but you can try.
https://www.cyberciti.biz/faq/linux-mount-cifs-windows-share/