As of Tesla software version 2020.12.5, you can view DashCam and Sentry Mode videos on the main screen in your Tesla. Tap on the Sentry icon when parked and choose the option to view.
With the 2021 Tesla Holiday update (version 11, 2021.44.25.4 or later), you can view DashCam and Sentry Mode videos from the quick launch area using the Dashcam application.
If you wish to export those videos or archive them off the car, you have two options. One is to just remove the Sentry USB storage device and copy the files to where you want, perhaps having two USB storage devices on hand to avoid having no active Sentry while you’re copying (while it is possible to have an adapter to copy to another device right in the car, this may take a while).
The other option can be fairly complicated. You could purchase a Roadie, which is basically a Raspberry Pi device with some software, or you could build your own Raspberry Pi device. The benefit here is the Raspberry Pi device is basically its own little computer with WiFi, so you can copy files off (as long as the USB port is powered) wirelessly. The Roadie device has its own iOS application that does this, although the app itself is limited in features. It is possible to configure the Raspberry Pi device along with other services on your local network to automatically copy files over, but that is fairly complicated and beyond the scope of an FAQ response. Please post a query to the Facebook group for more information, if wanted.
One iOS/macOS application that works very well for viewing Sentry Mode videos either from the USB storage device directly or copied elsewhere is Focus Dashcam Organizer.