Hello,

You will have to create the required fields newly on your case extended table and then create a report on it. There is some chance of using an Audit table, but I would not suggest you do it as its Audit and will have large performance impact.

Alternatively, also follow this link for any other ideas if you want - https://www.servicenow.com/community/performance-analytics-blog/how-to-create-a-historical-report-ba...