Copper powder amount dissoved in water
If you want 10 ppm copper in 2 liters of water, the best way to make it would be to start with some soluble copper salt, like $\ce{CuSO4.5H2O}$, make up a convenient concentration (like 1%), then dilute it to 10 ppm. 

As was mentioned in the comments, copper metal is not noticeably soluble in water. When rainwater washing thru copper downspouts leaves a blue stain on concrete, the copper metal is dissolving because of tiny solubility of copper oxides or carbonates. It might be 10 ppm, or 1 ppm in a lot more water.