need to change image URLs

hi,

after running an audit on my site, an error that I am trying to fix is all the image URLs that are over 70 characters. but since the URL field is greyed out on each image, I’m not sure how to change it. i have already read a ton of existing forums and already downloaded the search & replace plug in. I keep thinking I’m using it correctly but nothing is changing. for instance, i want to change the image URL: src=”https://www.microconstants.com/wp-content/uploads/2015/11/method-development-and-validation.jpg” to src=”https://www.microconstants.com/wp-content/method-development.jpg”

I select all tables and run the dry run which brings up a list of all the necessary changes. then i uncheck the dry run box and choose “save changes to database” but nothing is happening. I am unable to stream any tutorials due to high security at my job, so any step by step screenshots would be very helpful.