I have a little problem, because at the beginning I didn't leave the file location on external but on application. Now I want to have my Minecraft worlds on the Windows 10 version, but there are no files in the "minecraftWorlds" folder. Can someone help me how I can get the worlds on "external"?
Go to the settings and there you can set the storage location as external.
Will my worlds be lost then?
The only way is to move the world via Realm Server.
So first of all you need an Xbox Live account (no gold, just a free account) and then a Realm membership.
The first time use of Minecraft Realms is free. After a month it will cost.
If you have a Realms world so far, go to the editing area and scroll directly down until you arrive at a field where "Realms World Replace" is written.
At Realm you choose a world and then upload it. Once this has been completed, go to the main settings of the game, switch the memory from "Application" to "External".
Then you go back to the editing icon of your realm world, where your world uploaded from the application memory is now, and then download this world again. This time, this world is now on your cell phone memory, which you can then save in the file manager.
That's it, so you keep repeating it until you've transferred all of your important worlds.
Btw: if you also use your Xbox account to log in to an Xbox One or Nintendo Switch, you can download your world uploaded to Realms on the consoles. So you can use Realms as a kind of cloud transfer storage.
I hope I was able to help you largely.
Cheers. ✌️
And is that really the only method?
Unfortunately yes.
And if I just change the file location to External, will my other worlds be lost?
No, but then they are temporarily not visible.
What is it like when I start the Realms Plus free phase? Is this simply ended at the end of the free phase or can you cancel something?
Membership continues, as soon as you have spent the first month for free, you have to pay afterwards. To prevent this, go to Microsoft.com, log in with your Microsoft account, and go there to all current memberships. You can manage or cancel membership for Realms / Realms Plus. If the subscription is terminated, it will continue to run until the day on which it is to be extended. From there, everything you had with membership on will be deactivated.
In other words, your subscription will not be canceled immediately, but only on the day it should actually be extended. But for that you lose access to all texture packs or worlds, already created worlds of them or currently used texture packages are blocked until you subscribe to Realms Plus again, or buy one of the TP or mashup packs.