Milli- means "one thousandth" so milliliters or millilitres means " thousandths of a liter or litre". 3,685 ml=3685/1000 liters or litres. This is the same as 3.685 l. So it's neither bigger nor smaller, it's exactly the same!
To understand the metric system (based on powers of ten) you just need to know the meaning of words like kilo, which means 1,000, mega, which is a million or 1,000,000, centi, which means a hundredth, micro, which means a millionth, etc. These prefixes tell you what numbers to divide or multiply by, and it's just a question of getting used to them. A dictionary will help!