0.00000604 = 6.04 × 10 ⁻⁶
Numbers in scientific notation get written in the form 1.23... × 10ⁿ, so it's a matter of counting how many times you multiply or divide by 10 in order to move the decimal point to the right position.
The number 0.00000604 has 3 significant digits, so you want to end up with 6.04, and to do that you need to move the decimal point 6 places to the right:
0.00000604
= 0.0000604 × 10 ⁻¹
= 0.000604 × 10 ⁻²
= 0.00604 × 10 ⁻³
= 0.0604 × 10 ⁻⁴
= 0.604 × 10 ⁻⁵
= 6.04 × 10 ⁻⁶
