Unable to install module pm2: - Failed to run installation scripts

I do not know how to determine what version of nodejs? I dabble in command line but in the case of FreePBX, I depend more on the GUI. As I cannot see the GUI right now (due to pm2 issue) I would need to have some guidance in how to find nodejs version in use?
Most likely a simple command line string but, you will need to post it so I can run the string. Sorry, I am a novice.