These radios can't be decoded without physically having it in your hands. Your best bet, assuming you can provide ownership information of the vehicle each came out of, is to take them to a local Audi dealer where they will be able to plug them in on the bench and pull a code from the servers in Germany. My local dealer doesn't charge for doing that, but I think they're in the minority.
Your other option is a shop offering a decode service as they'll be able to get around the original coding.
I don't think it can be done online - only with the physical unit in the hands of the decoder. I'd ask local car audio specialists in the first instance. Worth trying Audi dealer - not like these units are a major theft magnet these days so as long as you provide some ID for you they may do it