Is 0.0034 100 times greater than 0.34?

No, it's 100 times smaller.

For every space 34 moves away from the decimal point, it decreases by 10 times.

For example 0.034 is ten times smaller than 0.34.

0.0034 is a hundred times smaller than 0.34.

0.00034 is a thousand times smaller than 0.34 and so on........