HI ​@Reza11 

If I am understanding correctly you would like to know how to view imagery of the Karun River?

On Planet University, we have an onboarding page that will give you an overview Planet, Planet’s satellites, and how to view and use Planet data. You can then apply this to looking for the Karun River specifically. 

For your use case I would recommend starting with the Introduction to Planet Explorer course; Planet Explorer is an online tool used to search and analyze geospatial imagery, allowing you to see change across the planet over time.