Cal here from Shopify, thanks for reaching out to us. It's unclear what you mean, so I'll need to ask a few questions just to gather some context on your business and give you the best possible answers.
Who is your supplier for your products? You will pay them to supply the products to your store which you sell to your customer. Your customer purchases from your online store using the price that you have decided to set in your admin for your products. To oversimplify this a little, your profit margin would be what the customer pays minus what you paid the supplier for the product.
In terms of how your get paid, that will depend on what payment methods you use to collect your customers' payments. I'd need more information on what you are currently using in your store to provide more insight into this. If you were using, for example, the Shopify Payments gateway, you would receive scheduled payouts of any transactions processed through the gateway, which you can read about here.
Great, so take note as to what the price of the product is to purchase from them, and then set a realistic product price for the product on your own website, bearing in mind to factor in shipping costs, etc. What you charge the customer minus what your supplier charges you is your profit margin.
If you're brand new to the world of dropshipping and you want to really understand the fundamentals, I'd suggest reading out Ultimate Guide to Dropshipping. It'll help demystify the whole thing and make sure you get off to the best start with your new business!