All of my dragons have opposable thumbs, with claws on them. They use them for grasping things.

As far as I know, there's no species of 'pure dragon' whose default form is human-ish bipedal; I know that whichever kinds capable of shapeshifting in general can take that form as a sort of convenience, especially when working with humans, but it's not their true form. So then you're basically just left with hybrid species who might have it as their true form, like others mentioned.