when you multiply (positive)powers of 10 (that is 10, 100, 1000,...) on a certain number, you just need to move the decimal point to the right. the number of movement is equal to the number of zeros.
example: 245 x 10
you can write 245 with the decimal point right? 245 is also 245. or 245.00 (etc.)
that means, since 10 has 1 zero, you will move the decimal point once to the right which gives you 245 x 10 = 2450.
example: 3.14159265 x 1000
1000 has 3 zeros, therefore, you will move the decimal point three times. so 3.14159265 x 1000 = 3141.59265
get it already?
for division, instead of moving to the right, you will move it to the left.
example: 2.1532 divide by 100
since 100 has to zeros, move the decimal point twice to the left. so 2.1532 divide by 100 gives you .021532
NOTE: you can always write a number by adding zeros to the right most or to the left most of the number but not in between the digits of the number.
example: 20.23 is the same as 20.23000000 also the same as 00020.23 and also as 00020.2300000
but it is not the same as 20.002300 and 2000.2300..