According to Google's AdSense program policies, you are allowed to place up to three ad units on each page of your website. In addition, you are allowed to place two search boxes and two link units on each page.
It's important to note that while you are allowed to place a maximum of three ad units on each page, it's not always the best idea to do so. It's important to strike a balance between monetizing your website and providing a good user experience for your visitors. Overloading your page with ads can be annoying for visitors and could potentially drive them away.
It's generally a good idea to test different ad placements and configurations to see what works best for your website.