Good call.
I always figure every used cycle I buy needs new tires (haven't been wrong yet).
Read through this section before you decide, and please, don't buy exact OEM replacements - there are much better tires available.
https://faq.ninja250.org/wiki/Tires
I've trashed brand new OEM tires with less than 500 mi on them because they sucked. It's not worth riding on questionable tires to me.
We had Pirelli MT75s and Pirelli Diablo Scooters on out Ninjas with 16" wheels, and the Diablos (cheapest) were better. That said, Pirelli's rubber compound isn't very good and dries/cracks too quickly.