We're all safe and doing fine, @pial. I hope you as well.
You can run and customize the Profit and Loss by Month report to show your monthly sales. Let me guide you through the steps.
Here's an article you can read for more details: Customize reports in QuickBooks Online.
Just in case you want to memorize this report, feel free to check out this article for the detailed steps and information: Memorize reports in QuickBooks Online.
Please let me know if you need clarification about this, or there's anything else I can do for you. I'll be standing by for your response. Have a great day and keep safe.