Two 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 two plus つ. So, this one is two things.
Since all of the "number of things" words all follow the same pattern (number plus 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 the kun'yomi reading, which means we'll have to use a mnemonic to remember them (you know the on'yomi reading of the kanji portion).
So what thing do you have two of? The two things you have are 2-foot tacos (ふた). How lucky are you, that your two things are 2-foot tacos? Other people only have two foot-tacos... And trust me, you don't want to eat those.
ビルが二つあります。
There are two buildings.
メロンが二つ川に入った。
Two melons went into the river.
二つのラーメンを三人でシェアした。
Three of us shared two bowls of ramen.