Answer:
To convert 1350 kilograms to micrograms, we need to multiply by a conversion factor that takes us from kilograms to micrograms. 
1 kilogram = 1,000,000,000 micrograms (by definition)
So, 
1350 kilograms = 1350 x 1,000,000,000 micrograms 
= 1.35 x 10^12 micrograms (in scientific notation)
Therefore, the mass of an adult rhino is 1.35 x 10^12 micrograms.