Need help finding a theme

I am trying to set up my first blog on my own domain. I know what I want it to look like in my head, but I can’t seem to find a theme to match my vision, and I don’t know html or css.

I want a simple layout with an image header that spans the full width of the page along the top 1.5-2 inches of the page. Directly under that I want a nav bar that is light in color. I want the body of the blog to be three columns that use the full width of the page. I want the right and left sidebars to be only slightly wider than the header is tall. I want the center column to fill in the rest of the space with only a wide enough margin between it and the sidebars to keep the page from looking cluttered. I want a plain white background. I don’t need a dedicated footer in the sense of a marked off space, but rather just a space at the end of the white page where I can put copyright and design information.

Does that make sense? Is there a theme that would be best to work with to reach my vision? One that will be the simplest to tweak?

I don’t have the funds to purchase a theme or commission one from a designer, so I am hoping someone can help me. I am interested in learning to code, but right now I just want to get things up and running.

Thanks in advance!