add_rewrite_rule with query variables

We have rewrite rules as:

for the URL – www.domain.com/app-api/v2/ecommerce/14. We load a custom template using template_include hook for custom rules.

The above works fine, but for some specific reasons the client wants to make use of query variables so that the new URL will be of the form www.domain.com/app-api/v2/ecommerce?pid=14

What I am trying to achieve is something like this, which doesn’t work.

What is the correct way to add a rewrite rule with dynamic query variables?