Creating a custom cart message based on order count

Hi LindStuart,

You can achieve that without an app. Follow below steps

1)create a collection and add product to created collection.

2)Create a discount “amount off” ad set it to auto discount.

3)select discount value to percentage and add 20%.

4)now apply it to specific collection and select here newly created collection.

5)Now in "minimum purchase requirement " set it to “Minimum quantity of items” and select there 3.

save it.