how do you get the big keypad on the apple watch for texting

You buy an Apple Watch Series 7. No other Apple Watch offers the Qwerty Keyboard. If you have a Series 7 watch, when you receive a text, you tap the response box and the keyboard comes up.

What series Watch do you have?

Is that true for the 41 mm watch or only the 45 mm watch? I was at Best Buy deciding which size of 7 to buy and the salesperson couldn't bring up a key board on the smaller 7 watch.