So I dyed my hair black a few months ago. And my natural hair color is coming in and I have blonde hair dye. But I don't know how to dye my hair back to blonde. Any advice?

Don't dye it blond! Do you want to look like you have a pumpkin on your head? Probably not ha ha. Highlight it over and over again and eventually it will become blond enough you can dye it all without it looking like a pumpkin.