Yes, you can use the same pixel on multiple stores, as long as the stores are associated with the same Facebook Business Manager account.
To use the same pixel on multiple Shopify stores, you will need to add the pixel to each Shopify store individually. To do this, go to the "Pixels" section of your Facebook Business Manager account and select "Add new data source" and then "Add a pixel." Follow the prompts to create a new pixel or connect an existing one.
Once you have added the pixel to each store, you can use it to track activity on your website or app across all of the stores associated with your Facebook Business Manager account. Keep in mind that you will need to set up custom conversions and events for each store separately to track their specific actions and behaviors.