Minecraft – Problems with an execute command

You have two mistakes in your command.

First of all, your target selector is wrong. Target selector arguments use a <argument>=<value> syntax, meaning it should be score_kills_min=1. A colon as separator is only used for data tags (which you aren't using in this command).

Secondly, the syntax for execute requires 4 arguments before the other command:

execute <entity> <x> <y> <z> <command …> 

Minecraft commands are dumb, they can not divine which arguments are not given when some are missing. In your case, the game sees the following arguments:

<entity> = @p[score_kills_min=1]
<x> = setblock
<y> = 195 
<z> = 56 
<command …> = -1199 minecraft:redstone_block

This is obviously rubbish and the command would fail. If you don't require <command …> to be run from a specific location (if you do, you know), just use ~ ~ ~ for the coordinates.

In summary, your command should be:

execute @p[score_kills_min=1] ~ ~ ~ setblock 195 56 -1199 minecraft:redstone_block

The /execute command is used to execute another command relative to something, the syntax you'll need is:

/execute <entity> <x> <y> <z> <command>

You should use target selectors with selector arguments to select to entity you want to execute from.

To summon TNT from an item drop, you could do:

/execute @e[type=Item] ~ ~ ~ /summon PrimedTnt

(Be careful with this command, as all item drops will act as a grenade)