In the Autohotkey help file or online documentaion, go to the Key List page (List of Keys, Mouse Buttons, and Joystick Controls), then scroll down to the Special Keys section at the bottom. This section may help with your problem.
The first few steps tell you use a script that is using the keyboard hook, then the bring up the AutoHotkey icon's Key History page. An easy way to do that is as follows:
Put the following script into an ahk file and run it with AutoHotkey.
When you run this script, the AutoHotkey Key History page will appear. You can press the key you want to test, then press F5 to refresh the Key History page.
Then you can follow the next steps from that section to find and use the key code:
Somewhere near the bottom [of the Key History] are the key-down and key-up events for your key. [...] make a note of the 3-digit hexadecimal value in the second column of the list (e.g. 159). To define this key as a hotkey, follow this example:
SC159:: ; Replace 159 with your key's value.
MsgBox, %A_ThisHotKey% was pressed.