The easiest way to do that would be to download Advanced Renamer. https://www.advancedrenamer.com/download.
Once Downloaded, open the app and click the "Rename Folders" Tab.
Drag all of the folders to that window and in the "Add Folder" settings, click "Add the Folders" and check "Add Root Folders"
Now click "Add Method" and click "Remove Pattern" and paste the text you want to remove from the folder name. In your case, MAME 0 225 CHDs merged_
Once you do that, you should see the changes in the "New Foldername" column.
Now click "Start Batch" and make sure all of your