@Gustavo80 

Hi,

Which username and password are you referring to?

If you are referring to the login username and password, it should be admin/admin by default. If you have ever change that, you can login to the router web console to change it. Below is the guide for your reference:

How do I change the administrative username or password of TP-Link device?

But if you changed the password but don't remember it now, you will need to reset the router to factory defaults as per this article.

If you are talking about the wireless network name and password, you can refer to this article instead.