How to load my pretrained network Keras model to use nengo_dl.Converter

Hello, good day!

I have a quenstion about converting a pretrained Keras network model into the one of nengo_dl. I want to convert Keras pretrained model into SNN using Nengo_DL.

I found that examples Nengo providing are handling the weights formatted as .npz, but I have only .pb file from the pretrained Keras model.
Can .pb file loaded as a weight file to use nengo_dl.Converter?
would I export the model as .npz file or convert into .npz file in other ways?

If someone knows about this issue, please give some help. It would be really thankful.