converting dra file to padstack

Hey myil17! Converting the file is not possible but you can export the padstack that you have modified (File -> Export -> Libraries). Then you can place the modified padstack wherever you want ... for instance, you can replace all existing padstacks of one type by this new modified one (Check the option in Tools -> Padstack -> replace ...)

I couldn't export the padstack. what I did so far is I opened a new mechanical symbol file and edited the pad out there(added some extra copper). what should i do next ? 

Ok, why don't you try opening Padstack Editor directly from Windows Start Menu and create a new file in the same folder as your PCB project. Then you can create/modify the padstack you need there. And then you can add it to any .dra file you create in that folder. Make sure that you have your padpath variable include all pads from the current folder (just add a dot to it ".").