Hello Sir, i can create products CSV file for importing in BigCommerce website also i have total 5 worker's team in my own office so we can upload all 4000 products manually with 100% accuracy as a new products, kindly PM me to get 10 products uploaded in your website as a test work and if you will like my test work than me and my team can complete all 4,000 in next 7-8 days, also payment release on 100% satisfaction only, thanks.