2^m = 0.04

$$\\2^m = 0.04\\
\mbox{when ever you are solving for a power you use logs (unless it is a very easy one)}\\\\
log\;2^m = log 0.04\\\\
mlog\;2 = log 0.04\\\\
m=\frac{log 0.04}{log\;2}$$

And you can finish it