How to get weights from another ONNX models

I have 2 ONNX model, the model1 is like: (conv1-pooling1), the model2 is like: (conv2-pooling2-fc2). How can I generate a new model3, which is (conv1-pooling1-fc2), weights of conv1-pooling1 are from model1 and weights of fc2 are from model2.