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Please see the official X‑Plane Support page for help.
I'm not with Laminar Research, just a fellow simmer in the UK, but you won't find a physical folder caller 'root' as it doesn't exist.
In terms of X-Plane 11, the 'root folder' refers to the X-Plane 11 main folder located in the 'root' of your C:Drive, or whichever drive you have chosen to locate the whole X-Plane 11 file structure.
As the X-Plane 11 folder/file structure is completely standalone, everything you need to find is contained within the X-Plane 11 folder as per the 1st photo below.
All existing aircraft will be installed in either of the C:\X-Plane 11\Aircraft\Laminar Research or C:\X-Plane 11\Aircraft\Extra Aircraft folders and all new aircraft should be installed similarly, please see 2nd photo below.
Hope this helps
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