Donor with infinite items in Minecraft pe?

I want to make a donor in Minecraft with infinite TNT with command blocks but how?

Here:

/ data merge block ~ ~ 1 ~ {Items: [{Slot: 4b, id: "minecraft: tnt", Count: 64b}]}

Just replace the coordinate.

That did not work

What exactly is not?
Oh well, the PE version, then I do not know, probably with / replaceitem