Hello Sakalam,
I think, there is no way (even not an easy one) of a massiv (or batch) change the Passwords by the camera itself (I have no NVR), because they are a major security funktion and should be chnaged one by one.
So IMHO, you have to take the important time, and change them one after another. OR find a programmer, who makes you a program, what makes "call IP -> login -> steps within (in the WEBIf) to the PW section -> change PW -> logout, next IP, and so on...
Greetings from cold Germany (3 C) to hot Oman (33 C)
42er