Open Windows Explorer, you can do this by opening up any folder or you can just click Start > User Name.
Click ‚ÄúOrganize‚Äù, scroll down and click ‚ÄúFolder and search options‚Äù.
Click the ‚ÄúView‚Äù tab. Scroll down until you see ‚ÄúHide extensions for known file types‚Äù, un-check this line here by clicking on the check box.
Click ‚ÄúOK‚Äù and now your file extensions will now longer be hidden.