Please help: transferring pst or ics calendar from Windows Lumia phone via SD card?

Hello,
I would like to be able to export 3 years of Outlook calendar from my old Windows Lumia 650 which isn’t synched to anything online, but only stored in the actual phone. I’m sure somewhere in the phone there must be a pst or ics file holding the data, since it’s all there on the device.
Is there a way of accessing the system files in a Windows phone and copying this ics or pst onto the SD card, so I can import it on my new phone (I got a Fairphone 3 plus)?
Any links, advice or tips very welcome.
Thank you

Could it be a solution to install NextCloud on your own computer and sync the lumia to NextCloud? I don’t know if the phone can sync to NextCloud.

I’ve never used a Windows phone, but just some ideas.

Have you been using a local account on the Lumia or a Microsoft account? If the latter, there’s a chance you can access the calendar by logging on to the Outlook web portal ( https://outlook.live.com ).
The “classic” Outlook desktop application allows export to a separate .pst file, whose location you determine. It’s possible that the Outlook application on the Lumia will allow that. Check out the details here.

There are also third-party tools, such as " Outlooktransfer ". I have no idea whether they work as you would expect and I am certainly not recommending any.
NOTE: the page linked includes a method for sending a calendar as an .ics file by mail. I don’t know whether that would be possible from the Lumia application. The method may also allow you to save the .ics to your SD card.