Convert 3GP to WAV

There are several currently available media editing programs and (online) converters perfectly capable of converting 3GPP Multimedia Files directly to WAVE Audio Files (.3gp to .wav conversion), which means you shouldn't face any difficulties attempting to extract the audio track (WAV) from a 3GP video file.

Some of the options you have, is using tools, such as FormatFactory or Freemake Video Converter, as these allow users to import 3GP videos and save their extracted audio track in WAV format.