i updated my Macbook Pro and cannot open iPhotos

iPhoto does not work on any of the 64 bit only operating systems. Photos replaced it many years ago.

Photos can convert an iPhoto library into a Photos one. Launch Photos with the option key held down. From the dialog, choose your iPhoto Library. Photos will create a new library with your iPhoto media. Your iPhoto library will not be changed, though it will be renamed.

Photos that aren't in albums just get placed into the library, jut like iPhoto. Since events don't exist in Photos, they are moved to an album. Did that not happen?

You can always try to convert the library again.

What format is the external disk? In needs to be formatted Mac OS Extended (Journaled)

I'm trying to convert an iPhoto folder on an external storage device. When I open Photos and try to select from "Other Library", I can't select the iPhoto file--it is grayed out and can't be clicked on or opened. This happened when I moved the file to my Pictures app, too. What am I doing wrong?