I had a program called Audiograbber installed on my old XP machine. It essentially let you grab any recording that could be played on the machine and saved it.

If I recall correctly I think there was some sort of add on encoder that was called Blade that encoded to MP3.

Have not used it for a long time so do not know what it is like now.

Seems it is still around

https://www.audiograbber.org/

Also had a program called Bitpim that I used to make personalized ringtones from any selected audio sound I wanted to use. Made various ones to assign to different callers so the ringtone let me know who was calling.  This was before the phones now that can be set to announce who is calling

http://www.bitpim.org/

Don't know anything about this other than it was the first thing that popped up in a web search when I typed in converting AMR files to MP3. So proceed with caution !

https://www.freeconvert.com/amr-to-mp3#