Hi there, p-greatland.

You can add the QTY column to the Sales by Product/Service Detail report. The total QTY of the items sold is shown at the bottom of the report. here's how:

1. Go back to your Sales by Product/Service Detail report.
2. Click the Customize button. 
3. Scroll-down to the Rows/Columns section, then check the box for QTY.
4. Click Run Report. 

Feel free to check out these additional articles for extra references: 

• Common Custom Reports in QuickBooks Online
• Export Reports, Lists, and Other Data From QuickBooks Online

Feel free to add more follow-up questions if you need more help with this.