First chose your tracks
then if they are in mp3 format use for example
this freeware tool : Free Mp3 Wma Converter V1.91
and restore them first to wav format.
Then with a version of wavelab or an Audio editor of your choice
you will convert them again to :
Extention : .wav
Audio format : mp3
Channels : (the same as source)
Sample Rate : 44100Hz
Encoding : LameEnc / 192 Kbps, 44100Hz Stereo
Here's a batch for the :Grossdeutscher_Rundfunk
http://www.zg52.com/zips/Grossdeutscher_Rundfunk.rar
and you extract it here :
Ubisoft\IL-2 Sturmovik 1946\samples\Music\Radio\Grossdeutscher_Rundfunk