iCloud sync too slow, how to undo?

I bought a new computer and tried to send my files to the new computer via the iCloud.

I foolishly dumped a bunch on the iCloud drive. What I saw happen was my files dissapeared from my old computer and the iCloud drive started to show sync icons.

Where did my files go? This sync has taken more than 4 days, and I want to try something else?

All my files are not on my old computer and they are not on iCloud drive. Where are they? I want to stop this process and put the files back and try something more robust.

I suspect there are temporary files someplace identifying my files to be moved, but how to stop and reverse this.

I'm more than willing to move what has been moved to iCloud and move the rest in another fasion. But how to stop the process and recover the "Unsync'd" data?