Hello,
Please read this article – https://xstore.helpscoutdocs.com/article/89-product-images
Theme Options > WooCommerce > Shop > Products Style > Stretch Product Image > Off
OR
Appearance > Customize > WooCommerce > Product Images > Thumbnails width > 542px, uncropped. After these changes, you need to Regenerate Thumbnails to apply them. You can use Regenerate thumbnails plugin to do this.
Regards