Thank you for reaching out to the Community. I agree with Fiat Lux - ASIA. Also in QuickBooks, you can include your product's SKU, quantity, class, amount, tax, and description.
As a workaround, you can indicate the unit in the Description field on the invoice page.
To know everything about these processes, you can check out this article: Add product and service items to QuickBooks Online.
Let me know if you have additional questions. Stay safe and have a great day ahead!