tell me airline and there fare from Karachi to Nanjing

There is no direct flight from Karachi to Nanjing, so you need to transfer in Dubai and Beijing.
The Emirates Airlines operates flights from Karachi to Beijing and for the domestic part, the Eastern Airlines and Air China have flights.

For the fare, it is hard to tell, because the price is changed based on the seasons. You can see the airlines official website for more detail information. Or you tell me your departure date and then I help you to check.