all the digits of a quantity are significant figures.
significant figures can be established by reading the number from left to right, counting the digits starting with the first digit that is not zero.
follow these steps to find your answer
1. 0 between non 0 digits are significant ,eg. 5302Kg (4 significant figures)
2. 0 at the beginning is never significant, only there to show the decimal, eg. 0.045g (2 significant figures)
3.0 at the end of a number is significant if it contains a decimal point, eg. 0.0500g (3 significant figures)