I’m want to copy some keyframe from one file to another, but in the other file where I want to copy that it shows an error “no animation data in buffer to paste” Please help !! 
Right. Each instance of Blender you have open has its own buffers. You can’t cut and paste from one file to another like that.
What you can do isturn your keyframes in one file into an action, and then append or link that action into the second file.