about minimum order quantity

Hi,

When you edit a product, you have the setting "Quantity per order". If you enter 3 int he first input field of that option, the minimum order quantity of the product will be 3.
If you want to do it at the checkout (meaning that the minimum is for the total quantity of the products in the cart), you'll want instead to sent the "minimum quantity" restriction setting of all your shipping methods or all your payment methods so that the checkout will force customers to reach that minimum or it won't let them finish the checkout.