is there a flight direct from Nigeria to hefei, and I want to be there on 31st Aug.

There is no direct flight available. You may fly to Dubai from Nnamdi Azikiwe International Airport first (about 7 hours). Then, fly to Shanghai (about 9 hours). Afterwards, fly to the city (about 1 hour). You are advised to book the flight ticket as soon as possible in case that the tickets should be sold out.
By the way, you can book flight tickets through TravelChinaGuide. You can contact them through bookingtravelchinaguide.com. Have a try! :)