@smu226 “I want to find a way to extract, in an unsupervised way, the positions of that object”
You cannot expect a neural network to output ANY specific target (e.g. x y positions or any function thereof) without having trained it to predict such outputs. Neural networks are a supervised learning technique. Thus, your options are:
1.) train the model with labeled examples
2.) Use a non-trained image processing technique such as convolving the target with the image or background subtraction, or perhaps clustering by pixel values if the color intensities are different.