Hi, I am a foreigner in Jinzhou and I want to visit Hong Kong, Please where can I buy air-ticket to HK?

There is no direct flights between the two place, so you need to fly to Shanghai first and then fly to HK.
It is suggested to book the tickets on the airline official websites or on https://www.travelchinaguide.com/china-flights/.

Hi Janet, thanks for your guidance. I think Shanghai is too far for me, can't I get a flight from Beijing international airport to Hong Kong?

I have not loaded my CreditCard, so I will have to pay cash at the airline ticketing office. Please can you give me any airline ticket office in Beijing?

Of course, you can fly to Beijing and then to HK.
I seldom buy airline tickets at spot, unless I have to make a urgent transfer in the airport. If I will make an urgent transfer in the airport, I will buy directly at the airport. In Beijing airport, the ticket office can be found at Departure Hall on F2 in T2 and Departure Hall on Floor 4 of T3.
If you have to buy at spot in the city downtown area, I suggest you to ask the airline company for their counters directly. Hong Kong Airlines and Hong Kong Express Airways provide flight to HK, so I think you may ask them directly.

Dear Janet, thanks so much...
I do appreciate your kindness..