I noticed that you clicked "Not Helpful" for my answer. The storage location of offline maps is indeed "C:\ProgramData\Microsoft\MapData". The reason why you can't see the folder is that you haven't turned on "Show Hidden Folders". Click "View"-"Show"-"Hidden Items" in the Explorer menu bar. Select "Hidden Items" and then you can see the "ProgramData" folder. Even if you don't turn on this option, you can copy the path of the folder to the address bar above and press "enter" to access the folder.
Now I understand your purpose, although you can view offline maps by installing the old version of the map and changing the system time to 2023. But as the software prompts, this offline map was updated at the end of 2023 and is no longer accurate, and cannot meet your needs for such a long journey. I'm sorry that I didn't know your purpose at the beginning and didn't tell you this information at the first time.
If you want to make such a long journey. I recommend you to use Bing Maps, or other more professional map providers. And it's better to use online maps, because offline maps may not be updated in time, causing delays in your trip. I understand that you may be concerned about the lack of network signal. You can find a provider that provides offline maps and download an offline map in case the network signal is lost.
If you encounter any problems when using your computer, you are welcome to post in this forum for help at any time. If you found my answer helpful, I wish you could mark it as helpful. This will help others in the community who are experiencing the same problem as you to find a solution better. Thank you for your community feedback and for helping us build a better community.
Best regards
Raylan-MSFT | Microsoft Community Support Specialist