Eight Things
numeral
This word follows the "number of things" pattern where there's a kanji for a number plus つ on the end. Whenever you see this, you know the word means "____ things." Knowing that, as long as you know the kanji (which you do) you can figure out what number of things it is. For this one, it's the kanji for eight plus つ. So, this one is eight things.
Since all of the "number of things" words follow the same pattern (number + つ), you really just have to remember the part before the つ (and then remember that the つ is in all of these). All of the readings are kun'yomi, and since you only know the on'yomi reading for the kanji, we'll have to use a mnemonic to remember them.
So what eight things do you have? You have eight yachts (やっつ). Go ahead and count them, drifting on the water. They're beautiful. Also, be sure not to be confused by this particular reading mnemonic. It includes the つ, even though the つ is outside the reading you need to learn (just makes things easier for you overall). Since you can see the つ outside, it shouldn't be too difficult for you.
八つの山
eight mountains
八つのキーワード
eight keywords
八つのタイプ
eight types
このカレーにはじゃがいもが八つ入っています。
This curry has eight potatoes in it.
キットカットが八つ、口に入ってます。
There are eight KitKats in my mouth.
うちのおばあちゃんはインスタグラムだけで八つもアカウントをもってるんだ。
My grandma has eight accounts on Instagram alone.