Location: Appearance > Customize > WooCommerce > Shop
Under General settings, you will have the following two options:
Products Per Page: It allows you to select the number of products displayed on each shop page.
Products Per Row: It allows you to select the number of products displayed on each row of the shop page.
(Note: The WoooCommerce option in the customizer will be displayed only after installing and activating the WooCommerce plugin)