Tranny Fluid

I have a 2001 Cavalier 2.2 engine automatic, if I pull the tranny pan and change the filter, how much fluid will it take to fill it back up?

You did not say what trans. May range from 3-4 up to 7-8 qts.
But you can measure what comes out or start with 3- 4 qt back in and keep adding untill full. Warm it up and recheck.
And always drive it about 10 miles and recheck.
The warmer the trans gets the lower fluid level will go.
MT.

It's a 3 speed automatic, how many quarts?

3-4-5.
There is no set qt. or know way know on what will drain out.
measure what comes out and put that much back in.
Or put 3 in and check it and add as needed.
That is what they put dip sticks or check plugs on the for.
Good luck
MT