How can i connect if i forgot the password

if you mean the modems password then its easy...
just press RESET button (see picture below) for 10 seconds
http://www.simplehelp.net/images/cable_modems/arris_cm450.gif
this should do a Hard Reset witch will restore all the factory settings as if you just took your modem out of the box...

now if you mean the Internet Connection password, you must call your internet provider, say your personal information (phone number, name, adress etc) and they will tell you a new password by phone, sms or mail (depending the provider)...

sorry there is no other way.

you try to create a new user name and new password
i hope i can help you