Before we start explaining you how to find the original audio files of your voice recordings on the disk, we’d like to mention that you can save your voice notes in a much easier way — using drag and drop.
If this doesn’t fit you, you can read the second paragraph and find the location of original .m4a-files on the disk on your MacOS Catalina or Big Sur.
If you ask me why search for them, I can say that first you can use this pre-installed app to make some narration and then you may want to use your audio files in FinalCut.