How can I use Cart and Checkout Validation Function to validate minimum order value?

Shopify Apps
2

You need to use buyerjourney step.

https://shopify.dev/docs/api/functions/reference/cart-checkout-validation/graphql/common-objects/buyerjourney

https://shopify.dev/docs/api/functions/reference/cart-checkout-validation/graphql/common-objects/buyerjourneystep