Hello Greg Kastanek
Currently New Outlook does not support importing the file you are talking about. Support for .pst files feature is under development and you can follow that link, New Outlook support for .pst files has been added to the product roadmap but not yet completed.
Microsoft 365 Roadmap | Microsoft 365
Also if your calendar is synchronized with your accounts such as Microsoft account, Google account . Then your calendar will be synchronized to New Outlook after your account is successfully configured. If your account is a three-party account using IMAP/POP protocol, it is recommended that you continue to use Classic Outlook.
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Have a nice day.
Sincere greetings
Forry.F - MSFT | Microsoft Community Support Specialist