How to change the ic_launcher_round.png folder content?

You can try to go on AnroidManifest.xml and change path

android:roundIcon="@mipmap/ic_launcher_round" 

to

android:roundIcon="@mipmap/ic_launcher"

The latest Android Studio generates round icons for you: Right-click the res folder, select Image Asset:

See https://dev.to/_s_farias/how-to-create-adaptive-icons-for-android-using-android-studio-459h for a more detailed walkthrough (Credit of @Guillaume Raymond).