You are only allowed to ask one question at a time so I have edited down accordingly. You can use the methodology below to answer all of your questions.
You are looking for conversion factors. Converting between different multiples of a gram is easy if you use the base unit of the gram as a common point between the two. First, convert 1 teragram to grams and then convert that number of grams into kilograms. For reference sake, 1000 grams are in a kilogram and a teragram has 1 trillion grams. Notice how the units cancel out to leave you with the desired unit (kg).
1 teragram * (1,000,000,000,000 g/1 teragram) * (1 kg/1000 g) = 1,000,000,000 kg = 1 x 10^9 kg
So there are 1,000,000,000 (1 billion) kilograms in 1 teragram. In scientific notation, this is written as 1x 10^9 kg.