After saving the model state dict like this: torch.save(model_par.state_dict(), 'model.pt')
In general, you need to do these steps:

Initialize the new instance of the model the same way you initialize it before training and saving, like: model_par= MyFancyModelClass(some_args_here)

Load state dict into model: model_par.load_state_dict(torch.load('model.pt'))