How to fix turn on USB storage in android

      Many android devices doesn't show turn on USB storage option when connected to a computer due to driver problems.

To fix this problem, We can use a simple app namely "USB DRIVER FOR ANDROID"

You can get this app from google play store using the following link.
                 USB driver for android

After installing the app,

1.Connect your mobile to computer using USB cable
2.Open this app.
3.Turn on USB debugging and MTP.

Now your mobile's internal & external storages are connected to your computer.