I am curious how you went from freelancing to working at a firm. I also got into development from a liberal arts background ( I went to a “great books” school )

I am curious how you went from freelancing to working at a firm. I also got into development from a liberal arts background ( I went to a “great books” school ). I started out several years ago, first with a brief internship, and then freelancing with a friend who a more experienced developer, and now I am freelancing solo. I have several sites and apps under my belt but I feel like an impostor and totally unqualified when I look at the requirements for various job listings (Junior/Intermediate JS/Python/PHP)