A completely dry and empty 4l60e transmission holds between 12 to 13 quarts of transmission fluid including the torque converter.
Have at least 13 quarts of transmission fluid on hand and then pour 5 of those quarts of transmission fluid in the 4l60e transmission.
Then start the engine up and let the transmission pump the fluid through it while the engine is running and then check the transmission fluid again and then while the engine is idling then add another quart and check the fluid level again.
Then repeat the process with the other quarts of transmission fluid until it's full but just make sure to not overfill the transmission fluid.
Overfilling the transmission fluid can cause transmission problems and transmission damage.