~3.5 quarts comes out if you open the drain plug on the transmission.
The full capacity is 7-7.4 quarts. Getting all the fluid out is more involved.
There's lots of threads on this topic. For example:
Tomorrow I am taking our 2011 CX9 AWD in for a drain and fill of the transmission. I was going to do this at home via the 3 qts at time routine, but without a transmission dip stick, I don't have an easy way to put fluid back into the transmission. So, I am just going to pay the transmission...
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