I got a job at the law school library.

Literal

Law-school [possessive-の] library [at-で] job [object-を] found

法学部 = 'faculty/department of law' (at a university). The で marks the location of finding, not the location of the job itself. 見つける (transitive, 'to find') vs 見つかる (intransitive, 'to be found').