What are the rules in changing scientific notation to standard notation and standard notation to scientific notation?

Here is the whole thing:
Lets pretend we are going to use the number:
12,645,000,000

• 1. get the numbers that are most important, which are: 12,645
• 2. see how many times you have to move the decimal point to make the number greater than 1 but less than 10. It would be like this:

start with: 12645
then move the decimal point over to the left 4 times, making it: 1.2645. this number is greater than 1 but less than 10.

• the number of times you moved your decimal point is your exponent of ten in the scientific notation. like this:

since you moved the decimal point 4 times, the scientific notation of this number is going to be your number-1.2645- times ten to the 4th power -10⁴-
So your number is now in scientific notation: 1.2645x10⁴
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To make your scientific notation standard notation, do the following:

1. look at your number: 5.8438x10⁵
2. move the decimal point over to the right whatever your exponent is: 5-8-4-3-8-0
3. your new number should be: 584,380
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IMPORTANT!
When your decimal reaches the end of your number, keep going! like this:
if the decimal point was here: 8.95 and you need to move it over 6 times, keep going! it should look like this:
8-9₁-5₂-0₃-0₄-0₅

so your decimal point would be 3 0's back and look like this:

895,000.

There you go!

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by the way, i am a 7^th grader.