Scientific notation is built upon the idea of moving the decimal place to the left or right so many places.
A foundational background concept is that multiplying by 10 makes a number bigger and moves the decimal to the right.
For example: 3.4 x 10 = 34
The counterpart for that is that dividing by 10 makes a number smaller and moves the decimal to the left.
For example: 3.4 ÷ 10 = 0.34
So, when you see 3.4 x 10^5, this means you’re multiplying by 10 fives times, so that will move the decimal point five places to the right.
3.4 x 10^5 = 340 000
On the other hand, when you see a negative exponent on the 10, then that means you’re actually dividing by that many 10s and will move the decimal point that many places to the left. (to make the number smaller)
3.4 x 10^-5 = 0.000034
So, you need to first identify if you’ll make the number bigger or smaller and then how many places the decimal point will need to move.