Connecting to a database with a containerized application

Good morning… I am really new to MongoDB when it comes to using it for app development.

Here is my question… I currently am developing an E-commerce application and in my limited training and research I was led to believe that to build my application to take advantage of containers, I needed to structure my database portion also in containers…

So… I spun up a free cluster and I made 7 databases, each with a collection that corresponds to a repository on my Visual Studio Project… Here is the example of my database structure.
User Database
user collection
Store Database
store collection
Product Database
product collection

this continues for all collections that I currently think I will need… My issue is in the .GetDatabase call on the instance of each Repository.cs file (UserRepository.cs)

 public UserRepository(IDatabaseSettings settings)
            _userCollection = new MongoClient(settings.ConnectionString).GetDatabase(settings.DatabaseName).GetCollection<User>(Collections.User);

The problem specifically is in the .GetDatabase(settings.DatabaseName) portion of the connection string.

My appSetting.json file contains the following:

"DatabaseSettings": {
    "ConnectionString": "mongodb+srv://",
    "DatabaseName":  "KLD9"

Now here is my question… For performance reasons… Is it necessary for me to have the individual collections in their own databases? If so… How do I make it so that each collection (user for users, and product for products) connects to their respective DatabaseNames?

Or am I confusing this… Is it possible to have all your collections on the same database but have multiple connections open to different collections at the same time provided you are capitalizing on async programming?

Am I over thinking this? Also… Is there some reference material that I can read (like the Aggregation pipeline manual)?