All Pakistani nationals are required a visa to enter Hong Kong. Since you are in China, and visas for entering Hong Kong abroad are usually handled by the Chinese Embassy, I am at a loss to tell you were to go.

Now, using common sense, chinese nationals go to their local PSB to apply and get the entry permit they require to go to Hong Kong.  So, I suggest you try going to the PSB in Shenyang and ask them where can you get a visa to enter Hong Kong, or if they can tell you where and how to get it.
I do know some nationalities can apply for a Hong Kong visitors visa on line, but I do not know if Pakistanu are included.
Good luck to you.

PS: Before exiting China, make sure your chinese residence permit does have a valid entry left !.

I'm sorry to inform you that you will be required to receive a visa from your home country for Hong Kong. The resident permit you carry means you reside or will reside in Mainland China for one year, it is no doubt multiple entry and China does not have the authority to give a non national a visa for Hong Kong. The visa that nationals receive are part of a different passport that is given when a visa is going to be obtained and even then they are required to travel with a tourist group their first visit.You could try two things

One: Visa upon entry of Hong Kong
Two: Pakistan Nationals do not need a visa for Maccau, you could try there