i'm trying to collect some information from my cameras using "Get item Configuration" and i'm not able to find one of the parameters asked for "PluginDefinitionId"

Configuration.Instance.GetItemConfiguration(AppGuidID, Kind.Camera, CamerasEncontradas[0].FQID.ObjectId);

If you use GetItem you will get the built-in kinds like Cameras. If you use GetItemConfiguration you will get Items defined by a MIP integration. So, in the context of the question you ask, using GetItemConfiguration does not make sense.

Trying to guess from your question what the best approach for you is, I think you want to see how a camera is configured. To do that you should use the Configuration API. I suggest that you as a first step explore the Config API Client sample.

https://doc.developer.milestonesys.com/html/index.html?base=samples/componentsamples/configapiclient/readme.html&tree=tree_2.html

PS. While as I mention I do not think you want to use GetItemConfiguration, if you want to explore a sample where it is central please see the Sensor Monitor sample-

https://doc.developer.milestonesys.com/html/index.html?base=samples/pluginsamples/sensormonitor/readme.html&tree=tree_1.html