Hundred-Hundreds | Commonly Confused Words

Hundred

/ˈhʌndrəd/

A number equal to ten times ten

The tree was probably a hundred years old.There are hundreds of beautiful women in the world.'You should not accept a hundred,' said Poirot.

This word has no antonyms

/ˌtʃɪltən ˈhʌndrədz/

Referring to the number 100 or the multiples of 100.

The library houses hundreds of rare books.She cooked for hundreds during the festival.Hundreds of stars lit the night sky.

Hundred is used when referring to the specific number 100.
Hundreds is used when talking about an unspecified large amount of hundreds or several hundreds.
If you are talking about more than 100 but not specifying exactly, hundreds is likely the correct choice.