How many Jews were killed in Poland?

If you mean 'How many Polish Jews were killed in the Holocaust?' please see the related question.

If, however, you mean in Poland literally, it is very hard to give an answer because:

1. Poland's borders were changed several times between 1939 and 1945.

2. The main extermination camps were all in Poland (pre World War 2 borders), and Jews were transported there from all over Europe to be killed.