The word you are looking for is ‘wooded hill.’
A wooded hill is typically characterized by its elevation, as well as a significant amount of trees covering its slopes. These hills often provide beautiful natural scenery and are great for outdoor activities like hiking and bird watching. The term emphasizes not only the physical aspect of the hill but also the lush greenery and biodiversity that the trees contribute to the environment.
In more specific contexts, you might also encounter terms like ‘forest hill’ or ‘woodland hill.’ However, ‘wooded hill’ is the most common expression used to describe such a geographical feature.