Hi Valeria! My name is David. I am a user of Microsoft products like you, and it is a pleasure to greet you.
The Respondus LockDown browser is compatible with Windows 10 and Windows 11 versions that are not in "S Mode" or "SE Mode". Therefore, when acquiring your Surface Pro 9, you should pay attention to the operating system it has, whether it is Windows Home or Pro. In this case, you shouldn't have any problems.
According to the Microsoft description for the Surface Pro 9, it should come with Windows 11 Home https://www.microsoft.com/en-us/d/surface-pro-9... Therefore, in the first instance, you shouldn't have issues using your browser. However, it's always best to be cautious when purchasing the product and ensure the Windows version that will be installed on the device.
Let me know if the shared information has been helpful. Regards.