Hi @iptsoe and welcome.
I’m afraid the bad news is that you’re going to need to rebuild them. Magento Frontend Development is completely “modular”. It’s a giant leap forward compared to what traditional web design looks like for your average CMS.
However, this makes it a real challenge to work with if you’ve never used the technology/methodology before. But the overall result leads to better optimisation and compatibility. It took me the best part of a year (on and off) to get my head around the basics.
The idea behind Blank/Luma is to reverse engineer it for your own purpose and build on top of it. This Official Magento U Course is supposed to make a great starting point. You should also check out the Official Frontend Developer Guide. I’d love to jump into this myself if my full-time job was just Frontend Development because I think I’d enjoy learning it. However, development isn’t really what I do.
Magento 2 Frontend Development is a highly sought-after skill. So, it’s one of those things that you could get certified for and charge a decent amount if you really wanted to get into it.