You may find old boxed versions on sites like eBay , often listed as "Vintage" or "Pre-Owned". Ensure the listing includes a legitimate, transferable serial number.
Because it is a "legacy" product, you cannot buy it directly from the Autodesk Store . Your best options for finding a copy include: 3ds max 9 buy
Trying to find how to purchase an old version of 3DS Max (2016) You may find old boxed versions on sites