Kreker gave the official correct answer. I do not know if these files will ever work when put on a new USB, however fatxplorer https://fatxplorer.eaton-works.com/ might be able to explore these files and allow you to extract the saves and copy them over to a new formatted usb. What I do know is the dev of this tool is very helpful, so please check the forums for your situation if itsit's recoverable (before purchase).
Due to my question required a feature not inplementedimplemented back then, he sendsent me a beta version to test and I was able to recover my files from a original xbox harddiskXbox hard disk and memory unit. This beta only worked for a month and now I also have to pay for it to fully function. There is a demo availebleavailable and maybe you can test if this would be something of use.
Easiest and cheapest would be getting that USB from your brother still. And yes, I would love to suggest a opensource tool, but I dont think "Xplorer360" would work. (itsit's a free tool, works on real hdd and full dumps)