Is there middle bus to rent for 10 adults from Pudong airport to Hefei?

Well, the distance between these two places is about 320 miles.
Maybe it's not easy for you to hire a private car because of the long-distance. If you insisit on the plan, try to drop an email to traveltravelchinaguide.com. I know they offer car rental service with driver.

If it doesn't work out, you are suggested to take airport shuttle bus line 1 to Hongqiao Raiway Station first. then change to a high-speed train to get to Hefei. The train ride takes around 4 hours on the way.
The ticket fare of first class seat is CNY188 and second class seat is CNY156.