Creative on survival multiplayer world

I have a mutiplayer world on survival, and i wanna know the seed.

For that i need to be in creative and have cheats enabled.

When i switch the gamemode from survival from creative, it doesnt change anything.

I tried stopping and starting the world, PLS help

No error massage, and /seed

If i do creative it would stay in the same world or a new one?

I downloaded the world, but when i do extract it tells there is already a file in this name.

Idk what happened but it is something weird, any idea?