The two terms can be confusing sometimes.

Found this site you might want to check out: http://examples.yourdictionary.com/examples-of-synecdoche.html

Examples of metonymy

• “England decides to keep check on immigration.” (England refers to the government.)
• “The pen is mightier than the sword.” (Pen refers to written words, and sword to military force.)
• “The Oval Office was busy in work.” (The Oval Office is a metonymy, as it stands for people who work in the office.)
• “Let me give you a hand.” (Hand means help.)

~~LMMolina