Step 1: Use the formula for charge in a series combination of capacitors:
For two capacitors in series, the total charge \( Q \) is the same on both capacitors, and the equivalent capacitance is:
\[
C_{\text{eq}} = \frac{1}{\frac{1}{C_1} + \frac{1}{C_2}}
\]
Step 2: Apply the formula for charge:
The charge on the capacitors is calculated using:
\[
Q = C_{\text{eq}} \times V
\]
Given the values of \( C_1 = 3 \, \mu F \), \( C_2 = 6 \, \mu F \), and \( V = 1000 \, V \), we find:
\[
C_{\text{eq}} = \frac{1}{\frac{1}{3} + \frac{1}{6}} = 2 \, \mu F
\]
Thus, the charge is:
\[
Q = 2 \times 10^{-6} \, F \times 1000 \, V = 2 \times 10^{-9} \, C
\]