Location depends on whether you’re on the Steam or Store version but first you must enable yourself to view hidden files. Once you have done that the store version can usually be found in C:\Users\Your username\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache
However you may have a different drive letter depending on your set up. If you used Steam it has a different path so use the search function.
Also check that all of your drives are using the necessary NTFS file system (this PC, right click, properties. exFAT is no longer supported (and actually never was)