Orn can be found in Hostelry Room #2 above the Timbre Timbers Tavern at (F-10). After talking with him, you can ask Furakku-Norakku for an extension, but it isn't necessary.
To save time, you may wish to purchase or obtain a Silver Beastcoin before proceeding. You may also wish to flag the quest A Crisis in the Making before heading out, as this quest also requires you to go to the Treasure Room in Giddeus.
The Library of Magic wants you to help retrieve its overdue library books. In this case, a Hume by the name of Orn has checked out the book "Art for Everyone," but has failed to return it by the due date.