Im making a wordpress plugin that works with WooCommerce and theres a feature im making than makes me need to know if an user is on the checkout page but i dont really know whats the hook or function for that, anyone can help?

I want a WooCommerce hook that can help to add string Contact for shipping quotes in front of Shipping Lable, by removing the shipping price on the checkout page. I’m developing a plugin and want to modify the shipping value.