Docker and Its storages

My question is with regards to containers and their data.
(Currently moved my ext.VHD from C:\Users\USRXXX\AppData\Local\Docker\wsl\data to Z:/ Docker Data)
I assume that now all the images and containers will be stored on the ext.VHD which has been moved to new location in Z:/Docker Data.)
Followed tutorial from (Move docker-desktop-data distro out of System Drive - DEV Community)

Further more, the main issue I face while still learn and understanding docker is that where are the root files for the projects I create.

Let me explain you.

  1. I opened my terminal with admin rights and ran Cd z:/docker-project, Mkdir DrupalSite, CD Drupalsite

  2. In the DrupalSite directory (created in step 1) I create a docker-compose.yml file using text editor.

  3. Opened my terminal and ran docker-compose up -d command.

  4. It successfully installed my Drupal (CMS project along with database).

  5. Now the real question where are root directories generated. There has to be a folder thats say htdocs etc where I can actually find the core files of the CMS.

The directory I created using MKdir in the first step seems to be empty when navigated to the folder.

docker-compose.yml

# Drupal with PostgreSQL
#
# Access via "http://localhost:8080"
#   (or "http://$(docker-machine ip):8080" if using docker-machine)
#
# During initial Drupal setup,
# Database type: PostgreSQL
# Database name: postgres
# Database username: postgres
# Database password: example
# ADVANCED OPTIONS; Database host: postgres

version: '3.1'

services:

  drupal:
    image: drupal:8-apache
    ports:
      - 8080:80
    volumes:
      - /var/www/html/modules
      - /var/www/html/profiles
      - /var/www/html/themes
      # this takes advantage of the feature in Docker that a new anonymous
      # volume (which is what we're creating here) will be initialized with the
      # existing content of the image at the same location
      - /var/www/html/sites
    restart: always

  postgres:
    image: postgres:10
    environment:
      POSTGRES_PASSWORD: example
    restart: always