@Alishba 

Which password can't you remember?

If you don't remember the wireless password, you can connect a computer to the router with an ethernet cable, then login to its web interface page to find the password for your wifi. You can follow this guide.

If you are talking about the login password, then the only option would be resetting the router to factory defaults state, then you can create your own login password for your own security. This is the guide to reset it.