Please see the attached document.
The Nikon D300s still have the USB connection, but it is no longer possible and also not necessary to put it into PTP mode. You can simply skip this step. Please verify that all the other settings are in line except the USB connection for your camera, the D300s does not need the PTP USB setting because it defaults to this when connected. Attached is the driver for your camera along with the installation instructions. In the software, with the LS connected, go to Scanner > Administration > Install and choose the E721 file.
Click here to download: D300 Installation Manual
Keywords: D300, manual