I finally found out how to export emails from Entourage 2008 to MS Outlook 365. In case anyone else has this issue, here's the scoop:

1. Drag an email from Entourage 2008 to the desktop. It will have the .eml extension.
2. Control (or Right)-click the email, click Open With, and choose MS Outlook 365.
3. Outlook 365 will open and the email will be there.

You can also do a Get Info on that file, change Open With to Outlook, and then click Change All.

try dragging a bunch of them to your desktop, then go select them all, and drag to the group of emails onto the outlook app

Doesn't work.