Answer
It will take 5 $\times 10^{9}$ years for the new sun to burn all the hydrogen.
Work Step by Step
The mass of the hydrogen in the Sun's core is given by
$m_{\mathrm{H}}=0.350 \times \frac{1}{8}\times M_{\mathrm{Sun}} .$
Also, the rate of burning of hydrogen is given in seconds, we need to convert that rate to years,
Thus, we will find how many seconds are there in a year.
Considering these amounts, we can calculate the time it takes for the hydrogen to be entirely consumed is
$$
t=\frac{m_{\mathrm{H}}}{d m / d t}=\frac{ 0.35 \mathrm{} \times _{8}^{1} \times \mathrm{} 2.0 \times 10^{30} \mathrm{kg}}{ 6.2 \times 10^{11} \mathrm{kg} / \mathrm{s} \times \left(3.15 \times 10^{7} \mathrm{s} / \mathrm{y})\right.}=5 \times 10^{9} \mathrm{y}
$$
