One way to think of numbers is by reading a numbers by the hundreds, tens, and ones.

For example,  356 can be read and written: three hundred  fifty six.

After understanding how to read the three digit number, understand the value in the context of the thousands, millions, billions, etc.

e.g

356,000,000 can be read and written:  three hundred  fifty six million.

356,000,000,000 can be read and written:  three hundred  fifty six billion.

356,356,000,000 can be read and written:   three hundred  fifty six billion,   three hundred  fifty six million.