Explanation

1 CGS SI $N_{1}U_{1} = N_{2}U_{2}$ $N_{1}\left\lbrack M_{1}L_{1}^{- 3} \right\rbrack = N_{2}\lbrack M_{2}L_{2}^{- 3}\rbrack$ $\therefore N_{2} = N_{1}\left\lbrack \frac{M_{1}}{M_{2}} \right\rbrack \times \left\lbrack \frac{L_{1}}{L_{2}} \right\rbrack^{- 3} = 0.625\left\lbrack \frac{1g}{1kg} \right\rbrack \times \left\lbrack \frac{1cm}{1m} \right\rbrack^{- 3}$ $= 0.625 \times 10^{- 3} \times 10^{6} = 625$