Karlie here from the Shopify Support Team! I've taken a look at the apps documentation and the app page in the Shopify App Store and I'm not seeing enough information on calculating shipping rates. Because of this, I would recommend reaching out directly to the app developers to inquire about what the app features are. You are welcome to do some research on your own and take a look at the Pirate Ship Help Documentation, here, or the app page in the Shopify App Store, here.
To reach out to the app developer, you can either us the 'Support' section of the app page in the Shopify App Store or you can follow the below instructions:
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!