Blocking my lost iPhone

I lost my iphone and there’s a new icloud signed in on it. But when I look it up on my icloud the device is still listed as my iphone or the icloud is still signed in. Then when i try to do the find my iphone it won’t show up. I wanted it to be blocked. So that the one who has it will not be able to use it. The one in the arrow is the one got i lost/stolen.