Hope you are doing great on these crazy times!
You can change all your shipping rate from the shopify admin. First go to Settings and click Shipping and Delivery.
From there you will need to click on Manage Rates:
Then you can adapt all of your Shipping rates and put conditions for free shipping.
If you need more help, feel free to reach me out.
I just take a more in depth look on your page. This look like a custom module and sadly there's no a copy paste solution. You would need to modify your cart.liquid to remove this function.
If is your wish, i can work on this. Reach me out to firstname.lastname@example.org so we can discuss further and solve this issue.