If you still have the original cards on a hard drive, you can start by importing the audio from the footage using Log and Transfer, then send the audio files to Compressor (using Send To -> Compressor), and then apply the MP3 preset to those clips in Compressor. (See Jeremy's answer here: https://forums.creativecow.net/thread/8/955419#1175318 )
If you don't have the original card, but have the Quicktime .MOVs, you should be able to similarly apply the compressor preset.
Note that this workflow (like MPEG Streamclip) will not give you timecode. If your client and/or their transcriptionist requires timecode, you'll have to approach this differently. Frequently an MP4 with visible TC burn is what they're looking for.