Quantum programming options
Does the customer (or you) have the Concept files? Concept made lots of files for a project, so it won't be just one file.
You can (maybe, see below) upload from the PLC using any of the comm ports (Modbus RS-232 or Modbus Plus on the CPU, Ethernet on the NOE). There used to be a PCMCIA MB+ card back in the days of computers with PCMCIA sockets. You can get a USB MB+ card, but it's not inexpensive so I'd guess that you would be better off with Ethernet.
Anyway, here are the basic options:
1 - Concept could create IEC programs and 984 Ladder Logic programs. On a Quantum, depending on the CPU, it could be either one or both. The 984 editor in Concept was quite possibly the worst 984 editor on the planet, so I'm guessing if you had used 984 you would remember that due to have the sort of fond memories often associated with dropping large heavy objects on bare feet.
2 - Assuming it was programmed in IEC Concept you may or may not be able to upload from the PLC. There was a project setting to download the source version of the project to the PLC, but of course that wasn't on by default when you created a project. It pretty much doubled the memory use of the PLC, which is probably why it was defaulted to off. If the project is in the PLC you will be able to use Concept to upload from the PLC. If the editor project is not in the PLC and you don't have the files, well, going thru pockets for loose change come to mind...
3 - That involves having Concept, or having access to Concept. Concept is a 16 bit application, so don't bother trying to install it in 64 bit Windows. Concept was also rather version sensitive, including service pack and hot fix numbers, so if you don't have the right one you may have an issue.
4 - If the system was done in 984 Ladder Logic and has no IEC then life is somewhat easier. You can upload 984 using virtually any program that can edit 984 logic. Modsoft (DOS), ProWorx (DOS), ProWorx Nxt (16 bit Windows), Concept (16 bit windows), ProWorx 32 (32 bit Windows) - they're all obsolete and no longer listed for sale according to my Schneider rep. You can buy Unity (probably the XL version since it's a Quantum) that will be able to edit 984, but only works with some of the Quantum CPU models. A 984 upload will have no comments or other documentation unless it was done with Concept and the download editor option was turned on. Programs downloaded via ProWorx of any flavor won't have any documentation.
5 - If you do have the original project files you have a slightly easier time. You'll need the project export file (it's got an extension of .ASC) and Unity can import that, mangle the hell out of the variable table, make some things work completely differently, and create a kinda functional Unity program. Of course you'll need a Unity CPU, which your Quantum may be (140-CPU-434 or 140-CPU-534) to actually use it. If the CPU is a 140-CPU-113-02 or -03 then Unity can't use it. If you don't have the exported file (.ASC extension) but do have the project then you can create it using tools with Concept.
6 - Don't forget that ALL Quantum CPU's are end of commercialization at the end of this year, so you can buy repair or exchange, or maybe somebody has one on the shelf, but otherwise the pockets and loose change thing comes to mind.
If you don't have Concept and you think it was done with Concept then I might suggest contacting your local Schneider distributor and Schneider rep. One of those might have access to Concept to be able to help you out. I do have Concept, so feel free to send me any questions.