The level and class required to meld to an item are the same level and class required to repair the item, which is listed on the item's tooltip. In the case of the Aeolian Scimitar, it takes a level 40 BSM.

If you don't want to grind that out, you can always find a 40+ BSM to meld it for you. No trading required, just right-click them and select "Request Meld." You'll need two Grade 3 Carbonized Matters in your inventory (since you're melding grade 3 materias), too.