I need to track the conversion in my online store

I have opened an e-commerce store and I have almost set up my online store. I'm not sure where to start advertising, but I'm starting to do outdoor advertising (https://dashtwo.com/blog/what-is-outdoor-advertising-and-why-is-it-important/). I want my clients to track through the conversion and for this I need the help of an expert. Does anyone advise me about this?