Right now the structure of the pages looks something like this:

I am trying to add a sub-page to the parent page.
My plan is to first just make a new page in the space.
And then using the command Update in the rest API to change the ANCESTOR of my new page to be the PARENT PAGE.
to be able to do the second step though, I need the ID of the Parent page. And this is where my problem is:
my Problem: HOW CAN I FIND THE ID OF A PAGE?
do pages even have ID's in confluence.
I do not see any API commands to be able to get data about child pages.
What I have tried the command :
GET /rest/content/{id}/child
where I inserted the number ID of the space . But I get an error message saying not found.

Summary: So I am not really sure how I can get the ID of the PARENT PAGE to be able to set the ancestor of my newly created page to be a subpage of the PARENT PAGE . [basically set the parent page as an ancestor of the new page]