How to recall a specific string from Firebase Database

I am trying to create an Xcode variable that represents the value stored under a specific field in a specific collection and document and I was wondering how I can recall the information

hello maybe this video can help you with your problem? https://www.youtube.com/watch?v=qA9L3_cK9Z0&list=PLMRqhzcHGw1ZsFRLAWa_Axx7daXteynjh&index=4&t=0s