Monaca allows you to upload your app to App Store Connect right from Monaca IDE. In order to do this, please do as follows:
When you successfully build a release version of your app, the
following screen will appear. Click on the
AppStore icon as shown in
the screen below.
Then, the App Upload window will appear. Click Next.
Fill in a valid Apple account information. Click Next.
app-specific passwords to the password field.
For details on how to obtain the password for App, please refer here .
Make sure you’ve registered this app with App Store Connect before uploading your app. Then, tick
We've registered the application with App Store Connect.. Click Upload.
The following screen is displayed for a plan that requires billing. Click Purchase.
The following screen will be displayed when the billing process of  is completed. Click Upload.
The uploading will start. Please wait.
If your upload is successful, the following screen will appear. It may take sometimes until the app shows up in the App Store Connect.
Now that you successfully uploaded your app, you can start selecting it in App Store Connect. Please refer to Selecting the Uploaded App.