Hi there, Bashir.

In QuickBooks, you have the option to utilize the Inventory item within the Product and Services section. Here, you can input the quantity of inventory you currently hold by entering it in the Initial Quantity on Hand field.

Here's how you can do it:

1. Go to the Gear icon.
2. Select the Product & Services.
3. In the New dropdown, click the Inventory item.
4. Complete the Basic Information and Inventory Information sections.
5. Add the initial quantity you have on hand.
6. Save once done.

Additionally, consider the advice from @SIAB and use a third-party solution that includes a Units of Measurement feature for seamless integration with QuickBooks.

Please don’t hesitate to reach out if you have any additional queries. We are available 24/7 to provide further assistance.