To Be Gone, To Run Out, To Be Lost, To Disappear
intransitive verb, godan verb
Here we have nothing, followed by the verb なる. A verb that means "become nothing"? That'll be to be gone, to run out, to be lost, or to disappear. This can be translated in various ways depending on the situation, but just remember that it always refers to something changing from being there, to not being there.
なくなる
This uses the kun'yomi reading, which you learned with 無し, so you should be good to go.
あ、トイレットペーパー、もうすぐ無くなるよ。
Oh, our toilet paper is almost gone.
することが無くなっちゃって、ヒマなんだよね。
I've run out of things to do and I'm bored.
正直、カード社会になってから、キャッシュを持つ必要性ってほぼ無くなったよね。
Honestly, since we've become a card-centric society, the need to carry cash has become almost obsolete, hasn't it?