Hi,
This request will require some custom code.
Actually the limit ca only limit the maximum of products in the cart, not the minimum.
The prices set as Mohamed said are only to have different prices depending on the quantity but it didn't restrict to a minimum of product to order.
In your case I think that the best way will be to use a plugin based on the function: onBeforeCartUpdate(&$cartClass,&$cart,$product_id,$quantity,$add,$type,$resetCartWhenUpdate,$force,&$do)
Then in this function, check the quantity of the added product, if it's less than desired, set the $do variable to false in order to not update the cart, and display a joomla system message.
Here is the link to the documentation:
www.hikashop.com/support/documentation/6...umentation.html#cart
It require some PHP skills