Cancel Catalog import (from Lightroom Classic to Lightroom CC)

Hi I trying Lightroom CC as a trial but I have already made a major mistake. I thought I would just import my Classic catalog into CC and that would be a good start however I have now realised that I don't want to do that as I have thousands of duplicates and other rubbish that I don't want on CC.

I have paused the sync but I want to cancel it completely but I cannot find out how to do that.

Does anyone know how to cancel the import and delete all the photos already imported? before I paused it had imported about 5000 out of 40000 photos.

I am using a mac running OSX