wordpress assign custom post on custom page
the default page for all the post is
archive.php
if you want to assign your own page for custom post page then use
archive-custom_post_name.php
whenever it will hit the url like
www.example.com/post_type=custom_post_name
it will will use your template
for single post page use
single-custom_post_name.php
the default page is single.php for all the post