Hello.
I do not know how is the tutorial, but I uses the following code on my custom plugins.
import { useFetchClient } from '@strapi/helper-plugin';
// on front-end component
// ...
const { get } = useFetchClient();
// request regular collections from content manager
get("/content-manager/collection-types/plugin::users-permissions.user?populate=*")
// request custom routes
get(`my-plugin/payments/to-do`)