Use the search bar on the IsaDub website to find "The Martian". You can type in the movie title and select the dubbed language (e.g., Tamil).
Here's a step-by-step guide to access and watch "The Martian" in IsaDub: the martian in isaidub
From the search results, select the link that corresponds to the Tamil dubbed version of "The Martian". Use the search bar on the IsaDub website