Mac Running High Sierra need Winclone 6

I have a Mac running High Sierra. I want to upgrade it but it is an iMac easy 2012 and upgrading requires that I delete bootcamp partition.

I would like to clone bootcamp partition to external drive then delete bootcamp on the iMac and upgrade. Then continue to use Windows on external thunderbolt drive

I have purchased Winclone 8, but it will not install on Sierra and the license key for 8 will not work for version 6. Any suggestions?