OT: Help with Broken Downloads Please

[Budge]

I have five GiP downloads of "Composer of the Week" from a couple of years
back which should have been .m4a files but are in my system as .mp3. 

Sadly they do not play and I am sure they are not .mp3 files.  These could
have been the result of one of my frequent errors but I would like
retrieve them if possible.

Running ffmpef on them gives me :-

Output file #0 does not contain any stream

Running ffprobe gives me:-

[aac @ 0x130e660] Error decoding AAC frame header.

They are all about 97 MiB and the above suggests to me they should be
recoverable if only I knew how!!!

Could somebody please help me with this.
Budge