How can you be sure that 9.9 ÷ 1,000 = 0.0099?

When dividing by 1,000, move the decimal point four places to the right.
When dividing by 1,000, move the decimal point four places to the left.
When dividing by 1,000, move the decimal point three places to the right.
When dividing by 1,000, move the decimal point three places to the left.