Mac restarted while copying 2TB between externals — Did files transfer?

[dmag]

I'm copying 2 TB of files between two externals over USB. It almost finished and then must have hit a glitch and the computer restarted. Now I see ghosted-out folders in the destination drive. However, they all register "zero bytes" when I get info.

Do I have to start all over from scratch, or is there a way to complete the job and save having to do it all again?

Thanks.