How can I access external video files on Android?

I am developing a Google Cardboard application that allows someone to view a video in a 3D VR space. Before the app enters VR, there will be a menu that allows you to select a video file before entering VR mode. Searching up how to access it on both this forum and Google doesn’t show up with any straightforward results. I have already added <uses-permission android:name="android.permission.READ_MEDIA_VIDEO"/> to the AndroidManifest.xml file. Any way to access the Media Picker app to get video files right from Unity?

Below is a screenshot of the menu I am talking about, with the files there edited out.