If you plug in the G3.... it should show up as a external device when you open Windows Explorer. What type of connection is it (MTP, PTP?)
Want the easiest way? Here is what I would suggest:
Enable the automatic photo backup (you can access it via Google+, which is still bundled with Google Photos).
Download and install Google Drive on your PC.
Go to drive.google.com, open the settings (gear cog in the right corner) and select "Create a Google Photos folder"
When you install Google Drive on your PC, you'll have a new favorite called "Google Drive"... which will have a "Google Photos" folder. When you take a picture or video on your G3, it will back up to the Google cloud, then once there, it will then automatically sync back down to your computer and you can just go into the Google Photos folder and find it.
No more cables.