The word you're looking for is [subdivision][1] (MW)

> one of the parts into which something is divided

Some example sentences:

>Dollars are subdivided into cents.
>
>Euros are subdivided into cents.
>
>The subdivision for the Dominican Peso is centavos; 1 peso = 100 centavos.
>
>Before decimalization, the British pound was subdivided into shillings, and then further subdivided into pence.


  [1]: https://www.merriam-webster.com/dictionary/subdivision