This iCloud feature will be gone when you update your Mac later this year.
When macOS Mojave is released to the public later this year, it will remove support for the Back to My Mac feature that allowed users to remotely connect to other Macs. Apple recommends iCloud Drive, Screen Sharing and Apple Remote Desktop.
Back to My Mac has actually not been in recent Mojave builds, and Apple did detail the removal earlier this month in a support document. Now, according to Brian Stucki, Apple is alerting users of the feature. The Remote Desktop app that Apple recommends, has not been updated since February 2017 and costs £80.
Apple now recommends relying on iCloud Drive for syncing files between other Macs, or using the Apple Remote Desktop. This is the last version of macOS to support 32-bit apps. Next year, Apple requires apps to be 64-bit only.