I'm 55 years old with a hemoglobin of 9.5 - how much of an Iron (Ferrous Ascorbate) 15mg + Vitamin B9 (Folic Acid) 25mcg Chewable Tablet should I take, and when's the best time to take it?

A hemoglobin of 9.5 does point to anemia that needs proper correction, so I'm glad you're looking into the right way to take this. How many tablets a day you need really depends on how severe the deficiency is and what your doctor's plan looks like, so it isn't something to guess at. As a general note, iron is often better absorbed on an empty stomach, though some people take it with food to ease stomach upset, but do get your doctor to confirm the exact dose and duration based on your Hb and how you respond.