Answer
$3.4\times10^{4}\,s$
Work Step by Step
Current density(J)= Carrier charge density(ne)$\times$Drift speed($v_{d})$
$\implies v_{d}=\frac{J}{ne}=\frac{2.0\times10^{6}\,A/m^{2}}{8.49\times10^{28}\,m^{-3}\times1.6\times10^{-19}C}=1.47\times10^{-4}\,m/s$ (Since we are not looking for the direction, negative sign of $ne$ is neglected.)
Time taken (on the average) =$ \frac{distance}{drift\,speed}=\frac{5.0\,m}{1.47\times10^{-4}m/s}=3.4\times10^{4}\,s$
