How can I use FFMPEG on windows for compression with multiple files at a time

I have discovered that FFMPEG is a thing and I’m wondering how i can compress many files in 1 bat file execution and that the newly compressed filed keep the same name as the Raw files and subsiquently replace the raw file in MP4 format

I am wondering this as i have over 700GB of Raw videos spanning over 3+ years of recording youtube videos (just for fun) and that my 2TB hard drive is now almost full lol

Thanks!
Ed