Hi,
I'm sorry to tell you that those are imitation pearls. In the 2nd photo, 3rd pearl from the top on the left, you can see where the imitation coating has peeled off, revealing the bead inside.
That doesn't mean the pearls aren't sentimental, though. I have some imitation pearls that used to belong to my late mother, that are not in wearable condition, but I can't let them go yet....
If you wish to wear your necklace, you could give it a gentle wipe with a soft damp cloth. Be careful though, as once fake pearls start peeling, more of the coating may come off.