Wifi password

[StealthG]

So my modem broke and i got and old one from a friend of mine. I plugged it in and it worked without any configuring. The only problem is that he has changed the wifi password and he cant remember and when i try getting into the setting by typing the ip adress on my my browser the username and password it asks me are not the default ones. Is there any way to reset them? And if there is, will that mean i will have to configure it again to acess the internet? Yeah i know im a rookie u dont have to say that. 
Thank you

[Prince32780]

Depending on the router can hold down the reset switch for a specified amount of time

that will reset the login username and password to default

 

what is the router model?

[StealthG]

the router model is: zte zxhn h108l  and the default username and password are both "admin"

i have already tried the reset switch and it didnt seem to do anything. I will give it another try.

[StealthG]

So i just rebooted the modem and tried the default WPA and it worked so thnx for the help