Hey there, surpomp2.
We understand that you are wanting to import one video from your iPhone 6s to your Windows 10 computer, but unable to do so. You can see how to sync content with iTunes here: Use iTunes to sync your iPhone, iPad, or iPod with your computer
If you only want to transfer a video, please follow the steps below from this article: Transfer photos and videos from your iPhone, iPad, or iPod touch
You can import photos to your PC by connecting your device to your computer and using the 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.
- If asked, unlock your iOS device using your passcode.
- If you see a prompt on your iOS device asking you to Trust This Computer, tap Trust or Allow to continue.
Then, visit Microsoft's website to learn how to import photos to the Windows Photos app in Windows 10.
If you have iCloud Photos turned on, you need to download the original, full resolution versions of your photos to your iPhone before you import to your PC. Find out how.
When you import videos from your iOS device to your PC, some might be rotated incorrectly in the Windows Photos app. You can add these videos to iTunes to play them in the correct orientation.
Learn what to do if you can't import photos from your iPhone, iPad, or iPod touch to your computer."
Let us know if that helps. Take care!