I want to perform the unity check if gameobject exists, how can I do that?

Unity tutorials explicitly say that "Gameobject.Find()" is a bad way to do the unity check if gameobject exists. It is very resource intensive and is not necessary! Take a Look at Adam Buckner's tutorial on this subject, "communication between scripts and game objects". You can find the article here:

https://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/communicating-between-components-gameobjects?playlist=17117

I know you may not be too concerned about efficiency at this point, BUT! as you polish this, you will become more and more concerned about it, and this will be a good habit to learn now, instead of attempting to fix a bad habit later!

Hope this helps!!!