Which api can get HS (Harmonized System) code of product, or order?

[Cindy27]

Customs information

Customs authorities use this information to calculate duties when shipping internationally. Shown on printed customs forms.

Country/Region of origin

HS (Harmonized System) code

[Jason]

Search the docs for "harmonized" and you'll find the relevant docs for both REST and GraphQL.
If it helps for narrow down results for product you'll be looking for inventory item endpoints.

[MaksimCPB]

GraphQL 

{
  productVariant(id: "") {
    harmonizedSystemCode
  }
}