Hi Danie,
As you already know, you can manually change the quantity on the bill. However, if you want automatic unit conversions, you’re probably better off checking the QuickBooks App store for a 3rd party solution. There’s bound to be a tool that can help you make these conversions like Katana Smart Manufacturing Software has a feature that converts your PO items into the desired measure that you want to track your raw materials. However, it should be mentioned that this tool has been built specifically for manufacturers.