I think you’re asking the wrong question. The better question is ‘How do I get my screenplay produced?’

I’m not an expert, but my understanding is that movie studios don’t really produce unsolicited screenplays anymore. You really need to produce it yourself, or be a known screenwriter who has prior relationships with producers.

If you don’t already have writing credits and an agent, you likely either need to produce it yourself – which means finding a director and actors and raising the money to pay for things – or you should try to publish it as a novel that becomes groundshakingly popular like The Martian or Dungeon Crawler Carl.

But the good news is that you can rest assured that having it stolen isn’t a risk you need to worry about.