Q: importing photos from iPhoto to photos

Don't use "Import" in Photos.  You just open the iPhoto Library in Photos to create a Photos Library from it.  Drag the iPhoto Library onto the Photos icon in the Dock to open it in Photos.

Sorry to sound stupid, but where do I find the iPhoto Library in Photos?

No problem, Suzette.

You select the iPhoto Library in the Finder, drag the library onto the Photos icon.  Then have a cup of coffee and wait. It may take a long time.

Photos will open on the new, converted iPhoto Library.  It will look very different from iPhoto. There are no longer events.  All your events will appear in the Album section in a folder "IPhoto Events".   See this help document:  How Photos handles content and metadata from iPhoto and Aperture - Apple Support

Let it run for a while. It can really take a long time, depending on the size of the library.  My current library with 40000 photos took three hours to migrate.

How large is your library?

If it really gets stuck -  his there anything unusual about your iPhoto Library? Is it on an external drive, perhaps a NAS or with a file system that is not MacOS Extended (Journaled)?

Do you still have iPhoto installed, so you could repair your iPhoto Library before migrating it?

For only 8500 photos it is too long.

If you want to try again, I recommend to rebuild your iPhoto Library before you try again.

Make a backup copy of the iPhoto Library before you try that. Copy the library to an external drive, just in case.

Quit iPhoto if it is running, then launch it again while holding down the options key, until you are seeing the First Aid Panel.

Start with "repair Permissions" and then Rebuild Database..

If you still cannot migrate the library to Photos,  rebuilding with the free trial version of iPhoto Library Manager will usually help.

Download it here:   http://www.fatcatsoftware.com/iplm/

And see tis manual page:

• Rebuilding a corrupted iPhoto library