upload all off my files iCloud files to dropbox

I'm trying to upload my current files from iCloud to Dropbox because my files were disappearing from iCloud, and I lost files that can't be replaced. Some of the uploads say it's going to take 5 days. Every time I try to perform a long upload, the estimated time is 4 days.  For one reason or another, the upload gets interrupted. If I start the upload over, am I saving duplicate files, or does it pick up where it left off? If it's saving duplicate files, is it possible to just restart the upload that was interrupted, or does anyone have a suggestion on a way to do this? One time the upload was disrupted because the power went dead on my computer. Another time, my dog stepped on my keyboard and by the time  I realized it, my upload activity had stopped. can someone please help.