That depends on what you already know about it. Formulas are just relationships between what you do know and what you don't know. I can't tell you what formula to use until you tell me what you know.
If you know the volume of the cylinder and its radius, then Height = Volume / pi xradius2
If you know the area of the cylinder and its radius, then Height = Area / 2 x pi x Radius
If you know the volume and area of the cylinder, then Height = Area2 / 4 x pi x Volume