Would you be able to help me I need to go from Shanghai Hongqiao Airport to Nanjing

Well, there is no public transport available at that time.
So you are suggested to find a hotel nearby the airport and start off in the next early morning.
Take subway line 10 to get to Hongqiao Railway Station, Exit E. Or just walk there; it takes about 10-15 minutes from the airport.
Then take direct bullet train to get to Nanjing. It takes around 2 hours on the way.
The ticket fare of first class seat is about CNY 230 and second class seat is about CNY145.