Hello Jacob,
Welcome to Microsoft Community.
Surface Pro 5G and Surface Pro Wi-Fi are two completely different models. The two models are equipped with different hardware, and the Wi-Fi version will not have any port to insert the Sim card:
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Therefore, I am afraid that this requirement of yours cannot be realized from the perspective of Surface. However, I have heard that there may be an external USB device (such as 5g USB Wi-Fi Adapter) that can be implemented, but its use and principle we do not clear, because Microsoft does not have the corresponding hardware products, these hardware products are from third parties.
Perhaps you could do some exploration in this direction to see if such external USB devices for ARM devices are available.
As a supplement, please read the following links carefully to understand the differences between ARM devices and other devices:
Windows Arm-based PCs FAQ - Microsoft Support
Best Regards,
Mitchell | Microsoft Community Support Specialist