So imagine you are playing with your building blocks and you need to know the size of your blocks to make sure they fit properly. That's what mesopotamians did too - they needed to measure things to make sure they were the right size.
But instead of using dimensions like we do today (like centimeters or inches), they used something called units of measurement.
One of the units they used was called a cubit, which was the length from your elbow to the tip of your fingers. So if they wanted to measure something really long, like a building or a wall, they used lots of cubits lined up next to each other.
Another unit they used was called a shekel, which was a small weight. They used shekels to measure things like food or money - kind of like how we use grams or dollars today.
The ancient mesopotamians also had a special unit of measurement for weight called a talent. Imagine a really big bag that is really heavy. Well, that's what a talent was like. They used talents to measure things like grain or precious metals.
So, just like you use blocks to build something, the mesopotamians used these units of measurement to make sure their buildings, food, and money were the right size and weight.