I'm now using Excel, from MS Office Professional Plus 2010. I'm trying to figure out the source of the data on a pivot table I received. Any suggestions?

When you select a cell in the PT a special tab appears on the ribbon called Pivot Table Tools
Click the Options Tab and click "Change data source"
You will now see it ( there are probably other ways)

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Using O365 v2503 - Did you know you can thank someone who helped you? Click on the tiny scale in the right upper hand corner of your helper's post

OK, thank...yes, that works.