wordpress父子页面url结构

I have a WordPress site and there are 3 main pages and 3 sub pages in each main pages. like

Stories
story1
story2
story3

When I click on Main menu the URL should be like www.domain.com/{mainmanu} (ie www.domain.com/stories and when I click on one sub page in this page, it should be like www.domain.com/stories/story1

I know I can have custom post type like %category%/%post_name%. But here these are pages (not posts)

How can I accomplish this ?

I think you need to set the parent property in Page Attributes. It is located on the right hand side of the page editor. For instance, for the Story 1 page, you need to set the parent to Stories.