I noticed lots of people wonder why there DCIM folder in the iPhone is empty, although there is a lot of pictures and videos saved in there.
DCIM folder can be accessed from windows explorer once you plug your iPhone, and typically, there you should find all the pictures and videos you have on your iPhone.
The reason is once the iPhone was plugged into the windows machine, it was locked.
Solution:
Unlock your iPhone
unplug it from the computer (if it was still plugged)
plug your iPhone again, making sure you can see your home screen and it’s not locked.