By default, copying from the command prompt will prompt you to overwrite files that already exist in the target location.
You can add \"/Y\" to say \"Yes to all\" re
You can make a text file with a single long line of "n" then run your command and put < nc.txt after it. I did this to copy over 145,000 instances where "No overwrite" was what I wanted and it worked fine this way.
Or you can just hold the n key down with something, but that takes longer than using the < to pipe it in.