Answer
$1.21\times10^6m$
Work Step by Step
Find the 'new' Earth radius by setting the acceleration due to gravity at the Sun's surface equal to the acceleration due to gravity at the 'new' Earth's surface.
$$g_{Earth new}=g_{Sun}$$
$$\frac{GM_{Earth}}{r^2_{Earthnew}}=\frac{GM_{Sun}}{r^2_{Sun}}$$
$$r_{Earthnew}=r_{Sun}\sqrt{\frac{M_{Earth}}{M_{Sun}}}=(6.96\times10^8m)\sqrt{\frac{5.98\times10^{24}kg}{1.99\times10^{30}kg}}=1.21\times10^6m$$