When you purchase a 'used' Inspire 1, how/where do you located the flight hours that the previous owner logged?

I want this informatioin for maintanence records.

Its stored on the internal sd card. You can download the data trough the aircraft usb port.

Pretty sure you can't find out, because total flight time is not displayed anywhere, you can look on the internal black box, but that will only have flight records up to max size of the SD card, older records are overwritten. Maybe this is stored somewhere on a DJI server or in the root of the drone, but even if it is you probably can't access it.
I'm fairly certain it's not on the drone, if it is I'm surprised i haven't heard about it before now.