Apple - Stop Docker from automatically starting on startup

Click the Docker icon in the right hand side of the menu bar, and click "Preferences". In the dialog that appears, untick "Automatically start Docker when you log in".

The locations are

cd ~/Library/LaunchAgents
cd ~/Library/LaunchDaemons

cd ~/Library/LaunchAgents
cd ~/Library/LaunchDaemons

But I recommend you just remove using launchctl remove

launchctl list | grep docker

launchctl remove com.docker.helper
launchctl remove com.docker.docker.11008