If he wants to run the exchange as legit as possible, securing licenses is one of the initial steps that he needs to embark on. And there's a lot more in it not just buying the code. I hope the OP realized what it needs to run a legit and decent exchange. Even after setting this up, there are a lot of things to do. Or if he wants to run a substandard exchange without any existing license under it, maybe he can. But in the long run, traders will not trust this exchange and so it will just bite the dust of crypto.
Technically, yes. But in the case of OP, it looks like he/she is going to need more experience in how startups work, rather than just-buy-the-code-and-run-the-exchange. I'm not saying that OP should give up on this goal, I'm just saying that he/she should calm down and start slow. Probably getting a job on a fintech company would give him/her a lot of knowledge on how things work in a company, rather than just going in blind.