/etc/php/7.0/mods-available/memcached.ini is in php-memcached 2.2.0-51-ge573a6e+2.2.0-2build2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | ; uncomment the next line to enable the module
extension=memcached.so
|