Good afternoon Richard Thomas,
Welcome to the Apple Support Communities!
If I understand your question, it sounds like you have updated your computer to macOS Catalina and are accessing the iPhoto library using the Photos application. Take a look at the resource below and look in the Documents folder and in the Pictures folder to see if the library is listed as a Photos library or an iPhoto library.
Before you make any changes, be sure to make a Time Machine backup of your computer. I don't believe you will find a duplicate library. But if you do, I would suggest dragging the library to an external drive to copy it first before deleting it from the Macintosh HD.
If you have multiple libraries, press and hold the Option key, then click the Photos icon on the Dock to make sure you are selecting the main (System) library on the internal drive.
Updating from iPhoto to Photos for macOS
Take care.