You can click Keep a Copy, because you're erasing your Mac later. You will be asked whether to keep a copy of your iCloud data on this Mac. If you're using macOS Mojave or earlier, choose Apple menu > System Preferences, click iCloud, then click Sign Out. Select Overview in the sidebar, then click Sign Out.
If you're using macOS Catalina or later, choose Apple menu > System Preferences, then click Apple ID. Learn more about deauthorizing computers used with your iTunes account. Then enter your Apple ID and password and click Deauthorize. From the menu bar at the top of the screen or iTunes window, choose Account > Authorizations > Deauthorize This Computer. If you're using macOS Mojave or earlier, open iTunes. Sign out of iTunes in macOS Mojave or earlier Make sure that you have a current backup of your important files. Moving to a new Mac? Before taking these steps, you can use Migration Assistant to move your files from the old Mac to your new Mac.
