We'll start with The Moon and I mentioned diameter not semi major axis which is simply the average distance from The Sun. The Moon's diameter is 3474.1 . One cubit = 20.62 inches ... 6,633,000,000 cubits = 136772460 inches

One meter = about 39.37

136772460 inches = 3474020.484 meters / 1000 = 3474.020484

Semi major axis is THE AVERAGE distance from The Sun.

I will leave it to you to figure out where you went wrong on 108,000,000