This project will convert a squarespace product list to a shopify one.
You can find your squarespace data here: [https://your_domain_name/api/1/commerce/products] (GET). This is easiest by going to your site, and logging into the config page: [https://your_domain_name/config] , logging in, then going to the previous rest URL. You should see lots of json data. Save that off into a file.
$ GoSquareToShopify square.json [output.csv]