Kassey here from the Shopify Guru Team! In your Shopify admin, you have the abilty to set manual shipping rates either by weight or by price. For weight based rates, you would set a condition based on the total weight of the order, you can see more about how to set weight based rates up here. Price based rates follow a condition based on the total value of the order, you can check out price based rates here.
I hope this helps, but if you have any further questions - be sure to reach out to Shopify support!
You can also check out the Multi Carrier Shipping Label app that allows you to handle shipping per item based on conditions like Zone, Quantity, Weight, Price, Total Weight Range, etc