Nature, in Wordsworth's "Tintern Abbey," transforms the speaker, changes him, helps him grow, leads to acts of kindness on his part. Nature also leads him to the sublime, creates in him a sublime mood. The speaker recollects nature during quiet or tranquil moments and it changes him and creates the sublime mood. The poem is more about the natural area around him five years before when the speaker first saw it, than it is about the area in the poem's present.
Coleridge's nature transforms into the supernatural to avenge a senseless and thoughtless murder of one of God's creatures in "Ancient Mariner." Nature controls the weather, creating fog or wind or calm on a whim. The sun disappears and the stars shoot out, sea snakes and a sea monster follow the ship. The supernatural is connected to the natural and the connection puts on a display that transforms the Mariner.
Wind is a transforming force in Shelley's "West Wind." It creates the trasformation from one season to the next, and Shelley hopes his poetry can do the same for intellectual thought. As the wind transforms the landscape and the weather, Shelley believes his poetry can transform the artistic world.
I've explained the role of nature in these three poems for you. I'll leave it to you to find the quotes--I can't do the entire assignment for you!