Dear cyberwillis,
Thank you for your kind reply.
Actually, I showed the image from MNIST data in the iteration and I confirmed that
every unit from the data in fact has a label and image.
However, because I cannot grasp with what format the dataset is formed from the binary(?) data,
it is difficult for me to create another dataset with the same format of MNIST.
Your another suggestion is also very helpful for me.
On the next step, I will see the tutorial and try to understand how should I create a Dataset class and load the data with it.
Thank you very much for your help:)