From where i can find the source code of cp command?

http://coreutils.sourcearchive.com/documentation/7.4/cp_8c-source.html

Go to this site coreutils Download the latest archive and go to /src/ there you can find the cp.c file(and many more)

cp is part of coreutils. There are also different implementations, for example busybox.

It's very strange that there is no cp on android. Have you looked thoroughly?

It is missing on my android as well.

You can work around by using:

  cat source > dest