Convert a classification ccn to a detection cnn

Hi, everyone. I trained a cnn to classify text from non-text using tensorflow. Now I want to use only the convolution layers that have been trained to detect these texts from images. How I can get only the conv layer (without the fc) to predict my bounding boxes. I actually read that it is possible to do this but I don't know how. Anyone can guide me pls.

classification cnn computervision detection