Managing Maximum Order Quantity
To be able to set the maximum quantity of a particular product per order, access the admin area of your website, and then move to the App Shop and Store tabs.
Find the Maximum Order Quantity module version 1.0.0 with a quick search, and install it on your website.
Once installed, go to the Products/Catalogue and Products (Brands/Categories) tab.
On the product editing page select the Main details tab.
To set the maximum amount of a product that can be purchased within a single order, specify the quantity in the designated field in the Details section.