Atlas cluster connection string

Lets say I have this connection string URI:


After replacing username and password and creating a MongoClient in the Vapor app and many http methods, which URL should I use in the Xcode app project, I mean which URL should I send post, get requests in order to get data?

Optional question:
Before submitting a Swift app to the App Store I have 2 projects, a Vapor that handles backend services using Mongo, and the Xcode app project itself, should I include the Vapor project somehow?