Where is my licens key and how can i find the account i bought it via?

Your license number will be found under the Products page of the Adobe account you used to register the product.  Did you purchase the product from Adobe or a third party?  How many Adobe accounts have you opened?

If you are still having difficulty finding the correct account, I suggest you try contacting Elements support. You can start a chat session by going to the Contact Adobe Support page and clicking on the chat button in the lower right corner of the page. Make sure you are signed into an Adobe account and try typing Agent when the chat window opens.