Answer
$L'=0.379m$
Work Step by Step
Length contraction states that the length of an object moving with the value gamma will have a length of $$L'=\frac{L_c}{\gamma}$$ The formula for gamma is $$\gamma=\frac{1}{\sqrt{1-\beta ^2}}$$ Using the value of $v=-0.9980c$ and $\beta=-0.9980$, gamma is equal to $$\gamma=\frac{1}{\sqrt{1-(-.9980)^2}}=15.82$$ Substituting known values of $L_c=30.5m$ and $\gamma=15.82$ yields an apparent length of $$L'=\frac{6.00m}{15.82}=0.379m$$
