Cannot see video files from File Explorer.

I'm new to Lumix cameras, so please forgive me for this basic question. I shot some videos on my Lumix G9 & I am trying to transfer them to my PC via USB cable. My OS is Windows 10. When I open the camera folder in File Explorer, it shows that there are no files. Yet the camera has the videos. What am I doing wrong? Are there codex to download?