Hi @margo141 
for per product “notes” when added to the cart, that’s done with line item properties.
For older vintage themes there’s this guide https://community.shopify.com/c/shopify-design/product-pages-get-customization-information-for-products/td-p/616503
If you need this customization setup for you then contact me for services
Contact info in forum signature.
ALWAYS please provide context, examples: store url, theme name, post url(s) , or any further detail in ALL correspondence.