The theme version can be found in two ways: WordPress admin panel or main style.css.
1. Theme version in WordPress admin:
Login to your WordPress admin panel and go to Appearance > Themes where you will find Divi. Click on it and, in the pop-up window that shows up, check the theme version:
2. Theme version in style.css:
Go to Appearance > Editor and it should open up the style.css file first. Search for the Version there: