Put back the media files in one folder

Hi. I wonder if it is possible to put back the media files in only one folder, not as I have nowadays in several sites where the media files are organized by months and years. I know I could disable this option in order to the files save as I pretend, but, how I would do with the previous folders already created? Can I revert this structure already created to put all files in just one folder through some plugin?

I was searching a lot but I haven’t had luck.
Thanks in advance
Fernando