I understand that you're trying to import your video from your iPhone to your Windows PC, but you're unable to find the video on the iPhone when it's connected to your PC. I'm happy to provide some help for this issue.
Instead of trying to browse the DCIM folder of the iPhone, I recommend following the steps in the article below to import your photos and videos based on the version of Windows that you have installed:
Transfer photos and videos from your iPhone, iPad, or iPod touch - Apple Support
Import to your PC
You can import photos to your PC by connecting your device to your computer and using Windows Photos app:
- Make sure that you have the latest version of iTunes on your PC. Importing photos to your PC requires iTunes 12.5.1 or later.
- Connect your iPhone, iPad, or iPod touch to your PC with a USB cable.
- You might need to unlock your iOS device using your passcode.
- You might also see a prompt on the iOS device asking you to Trust This Computer. Tap Trust or Allow to continue.
Then, follow the steps in these Microsoft knowledge base articles to learn how to import photos to Windows Photos app:
When you import videos from your iOS device to your PC, some might be rotated incorrectly in Windows Photos app. You can add these videos to iTunes to play them in the correct orientation.
Photos and videos that you sync from your computer to your iOS device using iTunes can't be imported back to your computer.
Additionally it may be that the video is already uploaded to iCloud Photo Library. You can check if this is the case on your iPhone by opening Settings > [your name] > iCloud > Photos. If you are using iCloud Photo Library, check out the following article to set it up on your Windows PC:
Set up and use iCloud Photo Library on your Windows PC - Apple Support
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