1- Move up a folder (to the root folder) in ES File Explorer and you will see a directory called data .
2- Go to data/misc/wifi folder and you will find a file named wpa_supplicant.conf.
3- Open the file and make sure you use ES File Explorer ‘s built-in text/ HTML viewer for the task.
4- Now in this file you will be able to see the network SSID and their passwords next to it.
5- Now note down the network name and its password
In this way you will be able to view all saved wifi password in android device.
Please do not edit anything in wpa_supplicant.conf as it can alter your device working or it will have affect on our wifi connectivity.