I'm setting up nginx as a proxy router for various APIs. How can I take a specific value form the incoming request and dynamically populate it into the upstream?

Request: https://api.domain.com/[resource]/v2/
Upstream: https://app.domain.com/api/[resource]/v2/

I this case, I want to take [resource] from the request and populate it into the corresponding [resource] of the upstream path.

Thanks