Typically any manufacturer, distributor, dropshipper, fulfillment house, etc. will define how data is imported and export. They should be able to provide you this upon request.
If your "vendor" is just another web site, they most likely do not have this setup.
It is your vendor's responsibility to provide data imports and exports. Even if your vendor runs one of the supported shopping carts we can not automatically create orders or get inventory from their shopping cart.
Example 1- We can automatically get orders from your site, generate a CSV file, and send that file to your vendor. It's your vendor's responsibility to import the order data into their shopping cart.
Example 2 - Your vendor can send you their inventory in a CSV file or any other support method. This is something your vendor needs to setup and prepare ahead of time.