How Do I Transfer Files From a Tascam Recorder To a MacBook Air?

HI, I am trying to transfer files (original music) for a friend from a Tascam DP-03 digital recorder to a new MacBook Air M2. I connected them via rca out of the Tascam to usb on the MacBook. I was told someone else had previously done this for him, exactly this way, on a different MacBook and it worked – but I can’t see the Tascam on the MacBook desktop. Is there some setting that I need to have on to be able to see it? I think if I could locate the files on the Tascam, then I could put it in Garageband and manage it just like I do on my iMac – except in Sound, in settings, all I see for input is MacBook Air Microphone – no other options. I appreciate your help. Thank you.
I am asking this question about file transfer because I can’t see a Tascam digital recorder file on the MacBook Air desktop so that I can copy it and work with it in Garageband.
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Greg