Menu: View→Interface Properties→Stan
Put a check mark here if you want Amos to ask you where to save the files it creates when exporting to Stan. Amos will ask you this question every time you export a model to Stan.
If you leave this check box unchecked, Amos will save the exported files in a subfolder of the folder that contains the model's amw file. For example, say the Amos model is in the file c:\work\abc.amw. Then the files that Amos creates when exporting the model to Stan will be saved in the folder c:\work\stanexport_abc.