Hi! Firstly, you would say 'I have been looking for my key for an hour' because it is an action that started in the past and continues into the present. For 'I have found my key' versus 'I found my key' both are correct but are slightly different. The present perfect (I have found my key) shows an action in the past (finding your key) that has a present result (you now have your key). If you chose this option, you are emphasising that you now have your key. The past simple (I found my key) is for a completed action in the past. If you chose this option, you are saying that the action of searching is finished. There is also a regional difference between these two tenses. In American English, past simple is used more frequently in cases where both the past simple and present perfect can be used. So, perhaps in the US, the past simple version would be more normal but in British English, the present perfect version would be more normal.