Unfortunately, there is No WooCommerce out of the box Admin/Customizer which allow us to change the number of products displayed in Shop pages.
By default, it will displayed the same number of products as ‘Blog pages show at most’ set in Admin Panel -> Left Menu -> Settings -> Reading -> ‘Blog pages show at most’).
So, in case you don’t add posts or number of posts can be same as number of products per page, you can change that value.
But in case you want to display different number of products per page than blog posts per page, there are a few options:
Option 1 (code change)
1. Login to your Admin Panel
2. Navigate to Left Menu -> Appearance -> Customize
3. Open functions.php
4. Insert the following code:
add_filter( 'loop_shop_per_page', 'new_loop_shop_per_page', 20 );
function new_loop_shop_per_page( $cols ) {
// $cols contains the current number of products per page based on the value stored on Options -> Reading
// Return the number of products you wanna show per page.
$cols = 9;
return $cols;
}
4. Save changes
Reference: WooCommerce Documentation
Option 2 (using a plugin)
We create a small plugin using the above code which adds a Customizer page with option to change that number.
The plugin is Free and it can be downloaded from WooCommerce.org: