i cant' backup or export my worlds on android

I have 86 worlds created in minecraft. But in the app storage of android.

Android/com.mojang.minecraftpe/files/games/com.mojang/minecraftWorlds exists, but shows emtpy.

The Worlds are not on my sd card. How can i save/export my worlds?

I thought if i change from app-storage to external storage. Minecraft moves the world

between that destinations, but it doesn't.

So i have no change to backup my worlds yet.