How do you write 0.00000038 in standard form?

To write 0.00000038 in standard form, you express it as a number between 1 and 10 multiplied by a power of ten. In this case, you move the decimal point to the right until it is after the first non-zero digit, giving you 3.8. Since you moved the decimal point 7 places to the right, you write it as (3.8 \times 10^{-7}).