How to Change WordPress Image URLs

I am facing a problem related to image URLs on one of the website that is bestappspoint.com
Most of the images in this site are with capital letters in URL (I didn’t know the consequences before) but now I want to redirect all the capital letter in URLs through .htaccess file or by adding a rule in SQL databases through phpMyAdmin. Please guide me the rule how to do it.
For example: One URL with capital letters is:

http://img.mywordpresstips.com/images/Talking-Speedometer.jpg

I want such all URLs to be redirected like:

http://img.mywordpresstips.com/images/talking-speedometer.jpg

In the lower image, URL has no capital letters. Can you guide me what .htaccess rule or phpMyAdmin should be added to solve this major problem so that there are no more 404 pages on my website.

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