The final volume will be 38.7 L.
We can use Avogadro's Law to solve this problem.
The volume of a fixed mass of a gas is directly proportional to the number of moles if the temperature and pressure are constant.
In a more usable form, Avogadro's Law becomes
#color(blue)(|bar(ul(color(white)(a/a)V_1/n_1 = V_2/n_2color(white)(a/a)|)))" "#
We can rearrange this equation to get
#V_2 = V_1 × n_2/n_1#
In your problem,