It is said that the virus can survive 24 hours on cardboard, and 72 hours on plastic. I just ordered some GI Joes, and they arrived in just 3 days, so I had to take extra measures. Here the postal service will not ask for signature, and at a distance, the postman placed the parcel in front of my door. I got the parcel, opened it, put the figures in very hot soapy water (that kills the virus) and left the box in quarante to be retrieved after 3 more days, to be ecological and re-use it.
Parcels that take longer to get to you, the contents are safe and you can just discard the package.
The more worrying thing is the contact with the postman, if he has it, and sneezes, coughs or simply virus are around him through his respiration, then you put yourself at (some) risk. After reading that the virus can be alive a few hours in the air, and a sneeze can move it up to 100 metres, I might consider picking the parcel from the postal office when I compulsorily need to go there to ship something, just to reduce risk.