Not sure what's going on, but I don't have a Prepar3D v5\Captain_Sim\757-III\Navdata folder.
Firstly, in your case the cycle info/data should be in the Prepar3D v5\Captain_Sim\navigation folder, not the Prepar3D v5\Captain_Sim\757-III\navigation folder
Secondly, the file names/types look wrong to me as well. As far as I know, the names and types should be:

Airports.db
Airways.db
cycle_info.txt
Fixes.db
IAPs.db
Navaids.db
Runways.db
SIDs.db
STARs.db

as seen in my attached image.

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