How to use the file manager to recover your passwords?
1. Go to Google Play and download a file manager application, such as ES File Explorer. You can also use one of the existing applications to recover the WiFi key, if you prefer.
2. After installation, open the ES File Explorer application and click on the menu icon, right next to the Home tab (upper left corner of the screen).
3. Go to the device and open the system folder. Another folder called etc. is located in the system folder.
4. Click and look for the WiFi folder.
5. Open the WiFi folder and click on the wpa_supplicant.conf file. From the options that are presented to you, you will have to select a text reader.
6. Once the text reader opens, it will show you a list with all saved SSID passwords.
Use of old passwords
Although you can recover the saved passwords, it may happen that it does not help you if the administrator has changed the password. In this case, the only solution is to ask the administrator for the new password. For example, if you use the WiFi zone network of a cafeteria and change the password.