Exporting data on device with no SD card
I have just aquired a Motorola MotoG which only has internal memory.
Trying to export a memento database I found that the export file showed on the phone using a file manager app but after connecting to my PC it did not show in windows explorer. I have seen many references to this situation in other forums.
Solution - shutdown the phone after exporting and then restart the phone before connecting to the PC.
Reason - Android is a unix based system and to see the file the storage has to be re-mounted onto the system.

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Jain Daugh commented
Even with having a File Manager app, locating a file and then copying it to a location that one could export with can be near impossible. Android is NOT very user friendly when it comes to files and folders.