How was your day, @Wendi?
I'm happy to guide you to achieve the information you need.
At this time, you can open the Profit and Loss by Class Report to get a month to month to previous year comparison. Just select the period you want to show and display the columns by Months. To compare the report to another period, select Previous period (PP) under the Compare another period section, then check the box before the % change to add the percentage of difference.
I've added these screenshots for your visual references.
This article shares the steps on how you can manage your reports in QuickBooks Online, you can read the details from here as an additional reference.
Once done, you can also read the topics from our help articles in case you need related links while working with QuickBooks in the future.
Let me know if you have any other questions. I'm a few clicks away to help. Have a good day!