How should I enable my terminal find command on the whole disk on macOS 10.13.6?
Make some tea and you’re done. That setting won’t arrive until you upgrade to a newer OS. 

Your find command has no barriers other than traditional ACL and permissions to stop it from traversing the entire disk. 


https://support.apple.com/guide/mac-help/change-permissions-for-files-folders-or-disks-mchlp1203/mac