I am trying to create checkout through checkout api, i am using npm modules https://www.npmjs.com/package/shopify-api-node
But i am getting error 403 forbidden.
Please let me know how we can use checkout api.
Your issue is that of OAuth scopes. You don't have permission to create those resources.
shopify-api-node, while it seems to support GraphQL, only supports the GraphQL Admin API, which does not support checkout creation (again unless you are a sales channel).
Your path forward is likely going to be creating a GraphQL Storefront API client by either forking or contributing to that library, finding an existing one, or creating your own.