You can find the password from VM instances console Log.
- Go to the GCP VM instances console at https://console.cloud.google.com/compute/instances
- Chose your Instance and click on the three dots → View logs
- It will open Logs Explorer up a new browser
- Run an empty query
- You will see a log entry like the following:
LAMP VM setup complete, your MySQL root password is 'xxxxxxxxxxxxxxxxxxxxx', change it ASAP!