No audio on imported avi files, and still no audio if I convert files to MP4

Hi. I have been filming a little footage using cameras that would only record in AVI. The files play with audio on Media Player but when I put them into Premiere Pro the audio doesn't exist any more. I have tried putting the AVI files through Media Converter to MP4 but it only produces MP4 files without any audio. I know the files definitely have audio recorded. 

Can anyone help, and has anyone else experienced the same problem?