A few years ago, I spent a fair share of time trying to copy files from and to a Macintosh Plus. I decided to use a 100 MB ZIP drive (actually two of them, SCSI for the Mac Plus and USB for a modern computer) and later a serial port connection with terminal software [1].
Now there's a much better and cheaper option: BlueSCSI [2]. It's a SCSI HDD emulator that allows to mount .img files stored on a SD card as HDD disks. It also supports CD and network card emulation.
Once the files are copied on a such a virtual drive, they can be extracted on a modern machine using via some kind of HFS explorer or an emulator.
Now there's a much better and cheaper option: BlueSCSI [2]. It's a SCSI HDD emulator that allows to mount .img files stored on a SD card as HDD disks. It also supports CD and network card emulation.
Once the files are copied on a such a virtual drive, they can be extracted on a modern machine using via some kind of HFS explorer or an emulator.
[1] https://blog.rekawek.eu/2016/12/08/mac-plus#hard-drive
[2] https://bluescsi.com/