Go to the Chrome extension menu by clicking on the 3 bars at the top right of your gmail, then choose Settings // Extensions.
Or type chrome://extensions in the chrome address bar
From the Extensions menu check the box Developer mode (1) then click on Update extensions now (2).
You can check the version you are using by going to the Chrome Web Store here: https://goo.gl/k4kGt5. The latest version is noted in the bottom right hand corner.