What we'd like to know is, password for what?
mIRC can have a password, some networks allow a password for nicknames, some for usernames. Specifics matter!
Please remember, NickServ and other nickname services have nothing to do with mIRC. They are 3rd party Services provided solely by the network that hosts them, they can be edited in any way and Khaled or anyone else affiliated with mIRC has no control over them. There are a number of different Services packages, there is no one "Services".
If it is a nickname password or username password you're trying to change, please ask in the network's #Help channel or check out their website.
You might also try out the following, assuming the network supports NickServ:
/nickserv help
/msg nickserv helpIt's often 'PASSWD' under the 'SET' menu, or 'SETPASS'.
Regards,