New Outlook doesn't yet have a file tab - it is coming soon (it's in the insiders builds) but that won't help you if you are looking for add-ins as new Outlook doesn't support addins.
Iif you are using an outlook.com or Microsoft 365 business address, you should have a button for Teams on the ribbon. If not, you can schedule Teams meeting in the appointment form. If you are using a non-microsoft owned address, you need to schedule the meeting from Teams.