I have light brown hair I put blond high lights in it then I dyed my hair dark brown I hate it so I used color oops now I want to dye my hair medium blond but my hair is still bark brown should I dye it?

If your hair is dark brown, you'll have a hard time getting it blond. Last time I tried exactly what you're thinking of, I had orange hair -_- (thankfully only highlights). If you want to dye it all, you may have to treat it more than once, or bleach it first. (I know this from personal experience, since most of my natural color is a dark brown)
Honestly, it may be easier (and healthier) to just wait until your hair grows back out or fades to something close to your natural color.