What could be the correct solution for Transforming a Complex request from one form to other? [closed]

I Have got 2 APIs, V1 and V2. V2 is the newer API, on hitting V2 API, I need to convert the request from Type V2 to V1 and hit V1 API, And the conversion itself is highly complex due to lot of business rules for converting from V2 to V1.

I need some kind of design pattern, or LLD using which I can solve this problem efficiently and also it should be highly extendable.

I have implemented using something like chain of responsibility pattern, as the request structure looks like a tree, and I will handle branch by branch from root the leaves.

I can't share the request here due to security issues.

Any advises here will be greatly appreciated, it can be anything like a framework, or the design pattern, or the LLD.