16 Hours Layover at Beijing Airport via Air China.

Hi,
I am having Pakistan Passport, and want to travel from South Korea to Islamabad with a layover period of 16 hours at Beijing Airport. I want to ask about transit G, Do I need to apply for a transit visa (less than 24 hours) or I will get my transit VISA at the airport immigration counter upon my arrival .? Airline has already reserved hotel room for me.
Thank you.