First, you'll need to get into the code editing space. For that click on:
1 ) Online Store
3) Then click the ellipses drop down(on the right side of the page)
4) Click 'Edit Code'
Next, in the left side bar, click on the folder Config, and then click on the file settings_schema.json.
The file will then open in the main window. At the top of that file, you'll find the theme name and its version: