First make sure you install all of the latest drivers for your controller then download a raw input program you may be able to see what "Special key" it is.
For example,I know in AHK "Media_Stop" corresponds to the stop key on my keyboard.
Or for programs that use ASCII helpful guides can be found with a quick google search.
1 Right stick 8 Start button
2 Directional pad (D-pad) 9 Right trigger
3 Left stick 10 Right bumper
4 Back button A A button (green button)
5 Left bumper B B button (red button)
6 Left trigger X X button (blue button)
7 Guide button Y Y button (yellow button)
(Source: support .xbox .com /en-US /xbox-360 /accessories /controllers )
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https:// autohotkey. com/ board/ topic/35848-xinput-xbox-360-controller-api/