3 of them.
5 significant figures.
there are 2 significant figures
There are four significant figures in 34.80 km.
There are 6 significant figures
2
3 of them.
It is the digit 2
3.774 is to 4 significant figures (count them)
1,000 m = 1 km If there is not decimal point at the end of 1000. it is just 1km. If there is a decimal point the correct significant figures would be 1.000 km
Assuming the final zero is not there for decorative purposes, 6 sig figs.
146.02 miles
All of those figures are significant. If you want to round it to 2 sig figs, that would be 13.