It's a totally new number of phone, the old numbers were disconnected and replace it with new one.
what changes should i do from voice router or from the Call manager server.
I am new in this field, please help!
That will depend on protocol used in your GW, and the dial plan config you're going to have.
This is not hard, but you certainly need to know what you're doing to do the change, and avoid causing problems with your current configuration.
Might want to reach out to a reputable consultant, or a Cisco Partner with UC specializations for this.
I have no idea what you mean by "configuration mode"
If MGCP, verify call routing and digit manipulation (if necessary)
If H.323/SIP, adjust dial-peers, or create new ones as required. Verify H.323 or SIP trunk config in CUCM, call routing and digit manipulation (if necessary)
Have your new DNs configured in CUCM.