All these options can be found under the theme customizer.
1- To open the theme customizer, go to your admin dashboard -> Appearance -> Customize
2- A list of all the theme customizer options will appear, navigate to WooCommerce -> Product Images
1- MAIN IMAGE WIDTH
Image size used for the main image on single product pages. These images will remain uncropped. Here you add the width you want in pixels without px, just write the width like for example 500.
2- THUMBNAIL WIDTH
Image size used for products in the catalog, this includes the shop page, categories, tags & search results page. Write the width in numbers without px.
3- THUMBNAIL CROPPING
This option affects all products lists, like the shop page, categories, tags, search results page, the related products and the upsells.