Switch Minecraft from Krative mode to Survival mode without cheats?

A few years ago I modded from survival mode to creative mode (via a mod that a friend installed for me). Cheats were off in the world.

Now I want to switch back to survival mode but since I no longer have the mod (whose name I don't know) I can't switch back.

Game mode 0 is therefore not possible.

How can I change the world to survival mode?

I look forward to your answers!

The whole you I think change files in the world

I don't think so

Open for the LAN.

You can find it in the settings. Then you can also activate cheats and reset the game mode.

If you are on PC, I have a trick: open the world in the LAN, cheats on and then open it in the LAN, and then you have cheats temporarily.

So I open the world and then open in the lan. Then cheats allow in game mode: survive and start the world. Then I enter / gamemode 0 but there comes: invalid command argument. Has the command changed?

Now I've done it! The command has been changed to / gamemode adventure.

Yes he has in the latest version it is now / gamemode creative the other things I do not know but will be displayed if you enter / gamemode