我是docker的新手，我正在尝试导出/备份我的wordpress db，但不知道如何在这里编写docker。yml文件

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: {}