About two million pounds of wheat were exported each year.
Literal
Every-year approximately 2-million pounds' wheat [subject-が] was-exported.
約 ('approximately') precedes a quantity to hedge it. ポンド is the katakana rendering of English 'pound.' 輸出される is the passive of 輸出する ('to export') — the wheat is the grammatical subject being exported. Past tense indicates a historical figure rather than an ongoing state.