Learn Intext Exercise 10.2 with Free Lessons & Tips

Terminal velocity is where an object reaches a velocity, where air resistance and gravity are equal, so acceleration stops.And the object continues at a constant velocity till it reaches earth or the aerodynamics of the object change by say deploying a parachute.
Without air, everything would accelerate at around 9.81 m s^2 on earth due to gravity. However, our thick atmosphere means that objects with large surface areas relative to their masses like a feather fall very slowly.
The theory was shown famously on one of the moon landings dropping a hammer and a feather together and showing that in the moons thin atmosphere, they fell at approximately the same speed.
Acceleration due to gravity on earth is simply 9.81m/s^2 at or near the earth surface.
If you want the accurate answer, you would have to take account for gravity weakening exponentially the further away from the earth surface you get.
If you want an even more accurate answer, you could look at the variations in earth gravity by location. I worked in a calibration lab in Aberdeen, and we had to correct all weight values by around 1% as the granite rock of the city is built on is so dense.
Funny Newton worked it all out because of an apple. It took thousands of years for any man in earnest to ask why do things fall downwards.