You applied the rule improperly. When dividing exponents, you subtract the exponent of the denominator <em>from</em> the exponent of the numerator, not the other way around. The exponent you should have gotten was 
Answer:
4000 nm
Step-by-step explanation:
Conversion from meters to nanometers: 1 meter is 1(10⁹) nm
Step 1: Convert 0.000004 to scientific notation
0.000004 = 4(10⁻⁶)
Step 2: Convert by multiplication
4(10⁻⁶) x 1(10⁹) = 4000 nm