This concerto, identified by its Köchel appendix number, is a genuine work by Mozart, showcasing his mature compositional voice and understanding of the bassoon's capabilities. It is characterized by its melodic invention and well-crafted structure.
Work on dynamic shading and the expressive delivery of melodic lines.
Bassoon Concerto in B-flat major (K.Anh.230a) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
Bassoon Concerto in B-flat major (K.Anh.230a) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.