Alarms can only be for something in the next 24 hours or on a repeating day schedule. So you have two options at this point. Reminders and a Calendar appointment.
Now there is one huge thing you should know about the difference between the two. Reminders only activate a tone ONCE. Calendar appointments will activate a tone till you shut it off or it times out. If it times out, it will use the built in snooze and reactivate in 10 minutes. So Reminders can technically be missed where Calendar appointments probably will not be.