Autodesk Civil 3d 2016 Serial 19

Our company purchased multiple seats of Autocad Civil 3D in 2017. We primarily use C3D 2016 as it is compatible with the majority of our clients. I got a new workstation and found that C3D 2016 was no longer directly available from my Autodesk account. Although I was able to find out how to install C3D 2016 from AVA, I am unable to find a serial number of product key to complete the installation. Can anyone help?

autodesk civil 3d 2016 serial 19

If the later, 2016 would be part of your license file so you could review your license file to get that serial # since the serial # would be the same for all versions. However you are not technically allowed to use that given version since its fallen off the radar as @Pola_S pointed out.. Its only there in your license file to give you more time to transition to a newer version.