Answer
13 million tons
Work Step by Step
$S+O_{2}$->$SO_{2}$
mass of Sulfur (in tons)=
$\frac{(26\times10^{12}gSO_{2})\times(1molSO_{2})\times(1molS)\times(32.07GSO_{2})}{(64.07gSO_{2})\times(1molSO_{2})\times(1 molS)}$
= 13 million tons