is there is any option to convert the mechancial symbol to package symbol..so then i can add refdes,pack pins and create psm
Yes there is. Open the mechanical symbol and change the Drawing Type under Setup - Design Parameters - DEsign tab, change Drawing type from Mechanical to Package. Then add labels for refdes etc. If you need to turn a mechanical pin to a connect pin then use Add - Text, change the class/subclass to Package Geometry / Pin_Number and then pick the pin, the text location and type the pin number. Repeat for all pins. When you save it creates the relevant psm file.