You can download it from this driver page.
Now you can enjoy the full performance of the most powerful graphics option in the largest MacBook Pro on Windows. The 5600M was recently introduced and is actually much faster than the other smaller GPUs, but it also costs a lot more.
In your long-term planning, you should also keep in mind that Apple will switch all computers to ARM chips in the future and that the use of Windows is not yet clear. But since the transition period will last several years, this is not a task that needs to be done immediately.