My 3CX was hacked.
I saw from log that hacker register extension 1000 but I do not have this extension!
How can I find which ip address to register extension 1000 and call out?
It is doubtful that the local police would be interested in becoming involved with your hacking problem. Most of these IP's belong to servers/providers located in places like Eastern Europe, India, or China. Tracking down who was actually using that particular IP (if it wasn't spoofed) is a time consuming chore, like trying to pinpoint where Spam is actually coming from.
You may be able to get some assistance from your ISP, but then again, they already know that this sort of thing is going on, but it is very difficult to stop, they might, however, provide some suggestions. You probably need to concentrate on increasing the security on your system/router/firewall. Upgrading to 3CX version 10, with it's much improved security features, would be a good start.