Need advice on integrating Amazon with Shopify

I have decided to go with FBM via a 3PL and need to integrate between Amazon > Shopify > 3PL (shiphero).

The shopify to 3pl part looks straight forward but I need some advice on how to integrate Amazon with Shopify so that the order goes from Amazon to shopify to the 3pl WMS for fulfilment and can send back the shipping reference to Amazon. Which app on shopify would I need to use for this integration?

I know about the Amazon MCF app but is this meant for fulfilling orders via 3PL? I’ve mainly found guides for how to integrate this so that orders are fulfilled by FBA coming from shopify but I’m trying to do the opposite flow.