More important than population figures, however, is the amount of foot traffic you’ll have for your retail location--because in retail, rental is a big part of your marketing budget. Why? Because it will be too expensive for you to advertise to become a "destination" retailer. Only the largest big-box retailers have that type of budget, so to build your customer base, you’ll need a prime location with a lot of foot traffic.
Eventually, people may drive more than a few miles to shop at your store. Starting out, however, you'll need to focus on location.
All the best.