How can you hide file extensions?

Hello i have a ton of pictures in seperate folders with the extensions .JPEG and i really hate that it shows. I have tried going to the finder and unchecking the show all file extensions, but it does not fix that issue. I also saw this in another topic but i haven't been able to understand it.

Open the Script Editor in the /Applications/AppleScript/ folder and paste in the following:

tell application "Finder"

set extension hidden of every file of entire contents of (selection as alias) to true

end tell

Select the folder enclosing the documents in the Finder, and press the Run button in the Script Editor. If they are enclosed by multiple folders or are at different levels in the folder structure, select the first folder which encloses all the documents.

(22397)

I don't know if it still works. Im also not sure where i put the folder. I have tried programs but they take away the extension and make the picture not open up then.

Please if you can help