Changing a few specific things throughout checkout

First of all, I have HikaShop Essentials and I LOVE IT. My customers are solely in America, so I have a few minor tweaks I need to make. On checkout, I have a box for Billing Information, but the fields are not in the order I'd like them to be. Right now it's:

First Name
Last name
Street
Post Code
City
Telephone
State
Country

I'd like to move Post Code and Telephone under the State and Country drop downs. I would also like to change "Post Code" to "Zip Code"

Lastly, I would like to change the value of the button at the bottom of the form to "Next" instead of "Register"

I am capable of making these changes, but when I went through the files in components/com_hikashop/views I didn't see any files that looked correct. Can someone tell me what file(s) I would need to edit to make these changes?

Thanks!

Perfect! Thank you so much.