Pivot table from different sheets located in different files

Hello,

I'm trying to make a unit pivot table from different files.
I succeeded to transfer the three sheets into one.
In the attachment you can see the three tables. In each one of them there is a row "project name", but I have values that are unique to each file.
Now I want that the rows of the pivot will be all the project name from all of the sheets. how can it be done?

Thank you.
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If you are using Excel 2013, then I think this can be done with Power Pivot tools. I don't know much about Power Pivot, but I think you can find help on the Microsoft website.

Regards,
Maria