The address is essential for getting mail and packages. There is the private lobby which any tenant has access to. If you are expecting a package, it is best to collect immediately after it is delivered. With so many apartments in the building, you are likely to come across one thief in the apartment. There are cameras to try to catch any bad actors, however nothing is guaranteed. The address should be written as follows:
Name
Unit Number
1665 Duffield Street
Pittsburgh PA 15206
Let’s assume that John Doe lives in unit 601, his address will be
John Doe
Apartment 601
1665 Duffield Street
Pittsburgh PA 15206
Some places may reverse the street, and apartment number around, but this will be how I would write my addresses. I even do this with my PMB, and get my mail well enough.