The ..._oci.dll is part of the Oracle C Interface. Unless you need to use Oracle, I suggest you go to the relevant line inside the php.ini file and uncomment the loading of this extension. However, if you need to use this extension, you’ll need to install the free Oracle Client libraries and add them to the path.
Oracle has a page where you can download the libraries needed for your setup work as expected and you can see here: Oracle Instant Client Downloads
Note: After you choose your operational system (Windows as in your answer) in download section you will see the installation guide in foot notes of the next page. For others OSs this process will work the same way.