By default audio files are saved inside directory C:\Program Files\MiaRec Business\Data\Recordings\
Location of audio files is configured inside MiaRec.ini configuration file (see option FileNameFormat inside section [Recording]).
Example:
[Recording]
FileNameFormat=C:\Recordings\%{setup-time#%Y%m%d}\%{setup-time#%Y-%m-%d-%H%M%S}.mp3
In above example audio files are stored inside directory C:\Recordings\.
Note: A default location of audio files can be overriden inside recording filters.
As you probably noticed, file path contains special parameters, like %{setup-time#%Y%m%d}.This is very powerful way of configuring audio files location. These parameters are described in details in article "File name format".