How do i export my database from docker

I’m new to docker and i’m trying to export/backup my wordpress db but not sure how to here is my docker-compose.yml file

version: '3.3'

services:
 db:
 image: mysql:5.7
 volumes:
   - db_data:/var/lib/mysql
 restart: always
 environment:
   MYSQL_ROOT_PASSWORD: somewordpress
   MYSQL_DATABASE: wordpress
   MYSQL_USER: wordpress
   MYSQL_PASSWORD: wordpress

wordpress:
 depends_on:
   - db
 image: wordpress:latest
 ports:
   - "3000:80"
 restart: always
 environment:
   WORDPRESS_DB_HOST: db:3306
   WORDPRESS_DB_USER: wordpress
   WORDPRESS_DB_PASSWORD: wordpress
 volumes: 
   - /Users/kentoj/Documents/projects/roze:/var/www/html
 volumes:
  db_data: {}

Run this command

docker-compose exec db mysqldump -u wordpress -pwordpress wordpress > dump.sql

Then delete first line from dump file. It is command line password warning.