How to capture requests of app on ios
I rely on Charles Proxy for web analysis. It's not clear if that's all you need - but it's a great start for many apps that call API.

How do you watch HTTP requests an iPhone app is making?

If you need actual packet capture, Apple describes how to do that on macOS / iOS / iPadOS and other operating systems here:

https://developer.apple.com/documentation/network/recording_a_packet_trace