I'm not sure to understand your request, but the numbers of JCPDS cards are those used to classify them in the crystallographic database. You should possess the database to find them or you can require this information for a specific compound and someone can provide you this number.
If you have a licensed copy of the Powder Diffraction File from the ICDD (formerly called the JCPDS), then you also have the software to search the database based on chemistry, structure, or other parameters.