@T_Janarthanan 

Hi, which password do you mean? 
If you mean WiFi password, after setup, the extender usually shares the same WiFi password as your main router.

If you mean login password of the extender on web interface or Tether App, it is admin by default, but if you have changed it when setting it up before, please use the new password you set to login.

If no any possible password, please try resetting the extender to factory defaults by holding reset button/hole for about 10s.