Units and Measurements Questions

Two full turns of a screw gauge cover $1\text{mm}$. Total divisions on circular scale is $50$. Zero error is $-0.03\text{mm}$. While measuring, main scale reading is $3\text{mm}$ and circular scale is $35$. The diameter of the wire is:

The respective number of significant figures for the numbers $23.023$, $0.0003$ and $2.1\times 10^{-3}$ are: