Here's a good place to start --> https://shopify.dev/concepts/apps#types-of-apps. I'd imagine you'd be looking to create a private app, assuming it's a one-time deal with a specific Shopify shop (i.e. - not being resold/reused with other Shopify shop entities. Here is more info along those lines --> https://shopify.dev/tutorials/authenticate-a-private-app-with-shopify-admin.
Hope this helps!