How to recover file extension (type)

I won’t go into details regarding the how, but I am at a position now that I have files with no extensions at all. Can I recover them and how? The folder that I fu had both mp3 and flac files.
And help would be highly appreciated.

There are both software tools and website services (upload the files) that can do that.
Should be easy to find if you do a web search on “determine file type without extension”.