Which folder has this icon:
That is the primary Pictures folder that the system created. Rename the iPhoto Library in each of the other two Pictures folder to iPhoto Library_2 and iPhoto Library_3. Move them into the Pictures folder with the camera icon above.
Delete the other two Pictures folders.
Now launch iPhoto with the Option key depressed and open the iPhoto Library. See how many photos are in it.
Next launch again with the Option key depressed and open the next library, iPhoto Library_2 and check its contents. Do the same with iPhoto Library_3.
If all of the libraries have photos that you want to keep download iPhoto Library Manager and launch. Add the three libraries to its left hand pane with the Add Library button. Then select the one of the three libraries in the left hand pane and go to the File ➙ Merge Libraries menu option. In the next window select all three of the libraries in the left window and New Library in the right window.
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The result will be a new library with a name of your choosing with all of the photos of the other 3 libraries. If you set iPLM's preferences correctly there will be no duplicates in the new library:
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Once you've checked the new library to make sure it's working satisfactorily and all photos are present and accounted for, you can delete those original three libraries.
OT