(2) China's land area is about 9.6 million square kilometers.

(3) My step is about 30 cm.

(4) The classroom door is 2m high and covers an area of 2m.

(5) The width of the blackboard is 9 decimeters.

(6) The area of a newspaper is about 44 square decimeters.

(7) It is about 200 kilometers from Shenzhen to Guangzhou, and it takes about 2 hours by car;

So the answer is: square decimeter, square kilometer, centimeter, meter, square meter, decimeter, square decimeter, kilometer, hour.