I have never sent a cold email in my life. Where do I even start?

Start with twenty companies, not two thousand. Pick people you can describe precisely (job title, company size, the specific problem you think they have) and write each of the first twenty emails by hand so you learn what makes someone reply. Keep it to four or five sentences: why you are writing to them specifically, the problem in their words, one line of proof, and a small ask like fifteen minutes. Your reply rate on the first batch will be embarrassing and that is the point, you are collecting evidence about your message, not building a machine yet. Only once a message reliably gets replies should you think about tools, sequences or volume.