Thanks for your feedback.
Please follow these steps to change the product image size as you want:
- Step 1: Navigate to Dashboard > WooCommerce > Settings > Product > Display > Product Image to add the image size as you want.
See this image http://imgur.com/icUkYFt
- Step 2: Install& Activate Regenerate Thumbnails plugin then go to Tools > Regen. Thumbnails to regenerate image.
Here is the link of plugin: https://wordpress.org/plugins/regenerate-thumbnails/
In addition, don't forget to check out this blog learn more about this:
Check it, then feedback to us soon.