Remember to derive natural minor scale from parallel major scale.

E major scale:

E - F# - G# - A - B - C# - D#

Using the formula 1 - 2 - b3 - 4 - 5 - b6 - b7 we get E natural minor scale:

E - F# - G - A - B - C - D

Other way to derive a natural minor scale is using relative major/minor method. Relative minor for a major scale starts from 6th scale degree. You can use circle of fifths to identify relative major/minor.

The relative major scale for Em is G major.

G major scale: G - A - B - C - D - E -F#

Starting from 6th degree we get E natural minor. The result is the same as with the first method.