Consulting advice on BigCommerce

We have an operating BigCommerce site. It is currently has 150 products for garment sales. It is not currently set up with SKUs. There are 6 size variants and approx 28 colour variants. There are rules for the colour variants for each product, that provide for showing different colour images for that product. We have recently changed our product coding system. However these changes when loaded cause the rules to no longer work. So it seems the rule is linked to the product code. We need advice on how to link the rules to the new product codes, using bulk update. We then want to import SKUs linked to the new product codes, also with working rules. Or is there another way to link the rules-based images to the applicable SKUs, so the rules are no longer required?. We can't find a link. There would be approx 19,000 of these. We will pay the escrow amount when the offered solution is proven to work by us.