The ASUS PRIME X570 Pro features a single x16 slot that connects directly to the CPU.
Check the accompanying documentation for the x570 reference. If not provided, you can reasonably rely on AMD's official press release materials.
Most boards feature the first PCIe port as X16, followed by a second port of X8 (similar pin count but half the width).
It's either an x16 for the highest position, or an x8 x8 for the top and middle positions (bottom remains chipset at x4 regardless)
Thank you for your clarification