In case you are using TYPO3 CMS:
You will not find the class TYPO3\Flow\Resource\Resource
there.
Therefore you are bound to Extbase classes. If you are using TYPO3 6.x, you might want to look either in the Extbase namespace or somewhere here: \TYPO3\CMS\Core\Resource\ResourceInterface
.
But most probably, the easiest way is to look for another tutorial on file uploads with Extbase.
If you're developing a standalone FLOW application, I don't have a precise answer.