We use connector 203456-0003 ，we want to know recommended standoff height.
Hello @thomas.yang and welcome to the NVIDIA developer forums.
This is a bit off-topic since we usually aim fro Software developers, but I can try to help you anyways.
First of all, which NVIDIA module is this? I assume Xavier, but which SKU specifically?
Since the connector is a standard part like for example one from Molex, I would suggest that this depends entirely on your carrier board design.
beyond that I really recommend that you bring this question up directly with your Original parts supplier, they should be able to answer all your HW related questions or forward them to the correct product channels within NVIDIA.