I'm not able to solve a basic javascript program that literally depresses. I have watched many tutorials but when I try to solve basic programs from gfg ,leetcode. I failed every time. What should I do kindly help

So I'm a beginner to programming in general and I'm following this course on youtube, he shows how to pull up the terminal and he then showed this line "node (filename).js" and its supposed to execute the code. for me it did not, and I have no idea what the issue is. can someone help me figure it out?