How can I server scaled images?

You can follow this step to set thumbnail woocommerce size

  1. Go to Appearance > Customize.
  2. Then go to WooCommerce > Product Images.
  3. Then go to WooCommerce > Product Images
  4. Write your desired width in “Thumbnail width” field.
  5. You can set the height of the images in “Thumbnail Cropping”
  6. Click on “Publish”

let me know the result.