Mozart's K.154a, "2 Versetten für Orgel," are likely short, contrapuntal pieces originally intended for organ. When played on the piano, they offer a glimpse into Mozart's compositional style of clear textures and elegant melodic lines.
Requires careful attention to balance between the melodic lines and harmonic support.
2 Versetten für Orgel (K.154a) 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.
2 Versetten für Orgel (K.154a) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.