Q: How do you recover iPhotos Events in Photos?

Photos does not have events like iPhoto had.   It creates Moments instead. Photos taken at the same time in the same place will automatically be grouped into moments.

The "events" you are seeing in the iPhoto Events folder are a fake.  They are actually albums.

When Photos migrated the iPhoto library it created an album for each of your old events to save the name of the event and the selection of photos inside. But it does not create similar albums for your new imports.  You have to create the albums on your own, if you want them.

Select all photos in the Last Import album and press the key combination ⌘N to create a new album for your recent import.

How do you recover iPhotos "events' in Photos?

How did you migrate your iPhoto Library to Photos?  Photos should have created the albums for your events as described above, when it opened the iPhoto Library.  Is the folder iPhoto "iPhoto Events" missing from your Albums section?

See this link:  How Photos handles content and metadata from iPhoto and Aperture - Apple Support