Unable to copy to Windows container ('docker cp') on Windows 10

Edit to Vimes answer as I had a difficult time to use the --mount within my docker run commmand. The actual run command needs to be within the quotes '' starting from type...

--mount 'type=bind,source="c:/host/folder/path/with/forward/slashes",target="C:/container/folder/path/with/forward/slashes"'

Based on a comment by @GregorySuvalian, I understand that Windows 10 allows Hyper-V runtime only. So my workaround is to stop the container, running the docker cp command and restart the container. (I preferred this over setting up a volume, since it is just a one time operation.)