Your welcome!
Hopefully I understand you correct. I found a great tutorial by Mandi Wise on which they she uses data from another service. https://dev.to/mandiwise/getting-started-with-apollo-federation-and-gateway-4739
You can check that code for a example on Github: https://github.com/mandiwise/basic-apollo-federation-demo/blob/master/films/index.js
Hopefully this helps you further 😉