Template for Custum Post Type

Hello,

I have created a custum post type with some metafields. Everything is working fine, except that't I am having some trouble creating the single file for the custum post. I want to maintain the header and footer of Generated Press and be able to change the inner layout.

I have tried things like single-mypostype.php or content-single-mypostype.php to see if at least I could get basic structure and then edit what I want, but when I accsess the URL of the Custum Post I only get that the page hasn't been found.

P.S: I am working with a child theme and tried single-mypostype.php and content-single-mypostype.php both in the theme and child directory. Which one will be the correct directory?

Thanks for the help!