astronmonical measurement

ok these questions are sort of linked and i really hope this question belongs in this board since it does deal with astronomy

**Question 1** In a scale Universe with the sun the size of a spherical grain of fine sand (diameter= 0.2 millimeters), how big a box (in cubic meters) would you need to hold all the stars in the Milky Way Galaxy. Packing efficiency of sand is a very complex problem, but assume that each grain of sand occupies 0.023 cubic millimeters.

i believe i got this one right and that the 0.2mm isn't used. here is what i got

200 billion grains of sand

Density of a grain of sand = 0.0023 mm3

200 billion x 0.0023mm3 = 460000000mm3

460000000mm3 = 0.46m3 (google.com)

The box would have to be the size of 0.46m3

ok but the next problem is tricky and I think i am really doing it wrong

**Question 1b** How big, in meters, would the Milky Way galaxy be in this scale universe? If the center of the Milky way was centered on Toronto, approximately where would the edge of the galaxy be? (eg, near Kitchner? Near Jupiter?).

I was told to scale the sun to a grain of sand so i have to use the 0.2mm from Question 1 to help figure this out

i really dont know if I am doing this right here is what i got

Milky Way = 100,000 light years in diameter = 9.4605284 × 1020 m

Sun’s diameter = 1,400,000 km (Taken from 100,000 light years = 946,091,000,000,000,000km

(100,000 x 9.46091E+12)

Sun’s diameter = 1,400,000 km

0.2mm

946,091,000,000,000,000km divided by 1,400,000km x 0.2=135155857142.857142

i really don't know what i did wrong here it seems that what i am doing is correct but this numer seems wrong so i am wondering if any one can help me with this question

soory again if this question does not belong in this board and in another one here