@Ashik.ur 

What password you are looking for? Wi-Fi password or the login password when logging into the router web?

For the Wi-Fi password, you can find a printed label underneath the router, where you can find the default wifi password if you never change it. If you have ever changed the wireless password, you need to connect a PC to the router LAN with an Ethernet cable, then log into its web page to find the password as follows:

How to find or change the wireless password on the TP-Link products

If it's the login password, you need to reset the router to factory defaults and create one if you no longer remember the existing password. Check this guide.