I want the block in these coordinates to be replaced with another block

I want a block called stoned sword that spawns at 3000 70 3000 everytime the player joins the world to be replaced with cobblestone when right clicked, if a variable called strengh(str) is over 999 and give the player a sword tool called blooded sword. I tried removing and placing cobblestone in its place if str was over 999 and the block was right clicked, and I did the same with the replace procedure, but nothing has worked. str goes up by 1 each time entity kills entity. I don't want the block stoned sword to be replaced if right clicked with the player having less than 1000 str. Please help I am an idiot. Thanks in advance.