it's almost similar to the place value of whole numbers, except it doesn't have the ones/units place and you should add -ths as a suffix.
Here are several examples, I will indicate the place value of the digit 1.
0.1 - tenths
0.01 - hundredths
0.001 - thousandths
0.0001 - ten thousandths
and so on...
For value, for example i have 0.123456789
digit - value
1 - 0.1
2 - 0.02
3 - 0.003
4 - 0.0004
5 - 0.00005
and so on... You just need to make the other digits zero.