Which literary device do you find in the expression?"She’s all states, and all princes, I, Nothing else is."

Metaphysical conceit is an elaborate metaphor comparing two apparently dissimilar objects or emotions, often with an effect of shock or surprise.
The given lines are taken from John Donne’s poem ‘The Sun Rising’ where the beloved and the lover are compared to all the states and all the princes of the world, rolled into one. This surprising comparison is a metaphysical conceit.
Source: enotes.com