I don't know where the idea of 'bestimmte Güter' comes from, but I'm guessing it might be from a regulation in some German-speaking country, because 'defined goods' doesn't sound typical in English, at least in my experience in AE. 'Goods' in general is a more old-fashioned, formal, or legal term, or at least tends to be used more for large quantities (wholesale) than individual purchases (retail).
If a particular subset of drivers delivers mainly individual purchases of food and groceries, then you could just say 'food delivery drivers' (Door Dash, Uber Eats, etc.) as opposed to 'delivery drivers' more generally (UPS, DHL, etc.), or of course 'truck drivers,' 'long-haul / long-distance drivers,' 'truckers,' etc. (drivers of 18-wheelers [AE]).
There are indeed some fixed phrases or traditional designations that contain 'parcel,' like 'parcel post' as well as UPS. But in normal conversation in AE, yes, the default for an individual item in my experience is 'package,' with 'packet' also an option for a smaller/flatter item in a shape like a bulky envelope.
On the company's website, it might use a term like 'item,' 'shipment,' 'order,' etc. to avoid describing a particular size or shape.
Not sure if that answers the question. See if others care to comment.