Duplicate a report with new Month data

I've tried your scenario using "Parameters". If you have same structure for all three months sales data tables, add an additional field to have a source field like March for March month and April for April or anything similar unique value for each source.

Then, append those three tables into a new table using "Append Queries as New" in Power Query Editor and name it as All (For example). Use this "All" table for building your dashboard. It will show all three months data in one dashboard, but you need to have one for each.... So add parameters with values March, April, May and filter the ALL table using the parameter value.

Everytime you change the parameter value, the dashboard will change automatically. Similarly, you can have duplicate dashboards as well pointing to different parameters. Here is few screenshots (Just with sample data)....

ParametersSample SourceFilter with Parameter value