I suggest downloading the free trial copy and testing it.
It's compatible with Snow Leopard.
It'll open versions 7 - 11 without any need for conversion (the file format is unchanged.) In fact the file extension is still .FP7.
It'll convert versions 3 - 6 though the older versions often require some additional repair before they're fully functional.
See this knowledge base article for more on the conversion of older files: http://help.filemaker.com/app/answers/detail/a_id/750/kw/migration