I assume you mean the common notation of: 
Simply think about the 10^y as showing how many zeroes you need to add to the first value. 10^0 means no zeroes, and 10^4 means 4 zeroes. 10^-2 would mean removing 2 zeroes (Sending it into the decimals).
The first value (which I refer to as X) is the form of the number before moving it up or down the decimal scale.
Example:
4.62 * 10^6
First look at the 4. This will want to have 6 zeroes after it so 4,000,000
Now we must consider it had "62" come immediately after the 4, so that makes it 4,620,000
Example:
6.21 * 10^-3
Again let's look at the first number, the 6. This time we don't want to add zeroes after it, we want to have the zeroes after it.
If we consider the number just before the decimal point as the default position, then you can count backwards 3 zeroes and find 6's new position
0.006
Once again, we know some numbers come after this. So let's just add those on:
0.00621
I assume you mean the common notation of:
Simply think about the 10^y as showing how many zeroes you need to add to the first value. 10^0 means no zeroes, and 10^4 means 4 zeroes. 10^-2 would mean removing 2 zeroes (Sending it into the decimals).
The first value (which I refer to as X) is the form of the number before moving it up or down the decimal scale.
Example:
4.62 * 10^6
First look at the 4. This will want to have 6 zeroes after it so 4,000,000
Now we must consider it had "62" come immediately after the 4, so that makes it 4,620,000
Example:
6.21 * 10^-3
Again let's look at the first number, the 6. This time we don't want to add zeroes after it, we want to have the zeroes after it.
If we consider the number just before the decimal point as the default position, then you can count backwards 3 zeroes and find 6's new position
0.006
Once again, we know some numbers come after this. So let's just add those on:
0.00621
