Permalinks Not Changing

I want to change my permalinks from /%year%/%monthnum%/%day%/%postname%/ to /%postname%/

but when I added the following to the .htaccess file, posts didn’t redirect the way I thought they would:

RedirectMatch 301 /dddd/dd/dd/(.*) /$1

What do I need to put into my .htaccess file to make it work?

My site is https://SweatingTheBigStuff.com