Get “Wineskin.app” on your Mac and install your Cubase 2.8 into that. It runs on a Mac and lets you use Windows programs that run inside it. You will probably not have any audio but you could at least open .all and .arr files and export the MIDI to a .MID file and the audio to .WAV., you can then import these into Cubase 7. You wouldn’t really need to export the audio as you will have all the wave files in your old projects but by exporting the combined audio (all tracks to stereo, with no fx, automation etc) you will at least have an idea where everything should go in the timeline of the project. Alternatively you can mute all tracks but one and export them that way, one by one but will be very time consuming for hundreds of projects with audio. Make sure you use Cubase 2.8 (in Wineskin) on your desktop or at least on your main drive as you cannot browse external drives.