/usr/lib/linux-tools/4.15.0-39-generic/cpupower is in linux-tools-4.15.0-39-generic 4.15.0-39.42~16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/linux-tools/4.15.0-39-generic/../../linux-hwe-tools-4.15.0-39/cpupower