I don't think you'll need to. Once you sign in to your Google account on the phone the contacts will be added. But if you need to add files to your Google phone you'll need to be in devoloper mode and enable USB debugging and set it to file transfer. Then your phone will show up as a drive.I have transferred my contacts to my Gmail account on my PC but I am not able to export it to the android phone connected with USB cable.
One more thing, go to about phone and tap the build number about 7 times and dev mode will be enabled.I have transferred my contacts to my Gmail account on my PC but I am not able to export it to the android phone connected with USB cable.