How to find the correct configuration and also the correct interface ?

[iKK001]

I am struggling with getting the correct configuration after opening the usbDevice.

How do I know how many configurations there are - and which one the correct one is ?

How do I know how many interfaces there are - and which one does have in- and out-endpoints ?

int configNr = 1;   // Q1: how do I know this number ?

await _usbDevice?.open();
_usbDevice?.selectConfiguration(configNr);
_configuration = _usbDevice?.configuration;

int interfaceNr = 1; // Q2: how do I know this number ?

_interface = _configuration?.interfaces[n];
await _usbDevice?.claimInterface(_interface!.interfaceNumber);