where is the UI pages for new GlideModal('UI_dialog_name')

[zhongL]

I tried the example provided ty reference, and it really worked out that seemed right.

But it turned out that I couldn't find out the UI page named "UI_dialog_name"

example of the reference(https://developer.servicenow.com/dev.do#!/reference/api/xanadu/client/c_GlideModalV3API#r_GMODV3-set...)

Is there anyone can tell me how can I find out the UI pages, thank you.