The BigCommerce API offers a few different ways to get product information, depending on what you need. If you need SKU-based stock information specifically, you can use the "Get a Product'sVariants" endpoint. This will return information on each variant of a product, including the SKU, price, weight, and availability.
Alternatively, if you need general product information (not specific to variants), you can use the "Get a Product" endpoint. This will return information such as the product name, description, price, and SKU, but not variant-specific information like weight and availability.
Both of these endpoints require an authentication token, which you can get by creating a BigCommerce API account. For more detailed information, including code samples, see the BigCommerce API documentation.