In addition to what Sharky said, basically you need to add in Postman what is called a Api Test which is nothing more than javascript and the Chai JS library.
You see the tests tab
You need to add this code in the test tab to filter out just the menu items of a given menutype. On my example site I have mainmenu and then I created using the API another site menu with menutype "menu", then added a menu item to it again via the Api.
Now I had:
mainmenu:
and
menu:
With the following js code you can fetch only what you want using the tests tab of a request.
pm.test("My custom site menu only items", () => {
const allMenuItems = pm.response.json();
const menuTypeToFilterBy = 'menu';
let onlySpecificMenuItems = allMenuItems['data'].filter((item) => {
return item['attributes']['menutype'] === menuTypeToFilterBy;
});
console.log(onlySpecificMenuItems);
//TODO: Do whatever you want with this filtered result
});