how we can determine the number of shell present in K L M N shell and the sub shell spdf

Shell number is n which starts from 1,2,3,4,....

If n=1, its called K shell, if n=2 its called L shell, and so on.

The first shell, n=1 has two electrons, the second shell n=2, can have a maximum of 8 electrons, if n = 3 , shell can have a maximum of 18 electrons.

This is calculated by the fomula  that maximum number of electrons that can be accomodated in a shell are 2n²

But keep this in mind , if any shell is the outermost shell it cannot have more than 8 electrons.Now the next part, To find the sub shell number:

It is denoted by a symbol l ,

the value of l depends on the value of n.

values of l = 0,1,2, .....(n-1)

l=0  s subshell

l = 1 is p subshell

l =2 is d subshell

l = 3 is f subshell

Now suppose we have the third shell, i.e. for the third shell , n = 3

then l will be equal to 0,1,2

SO, in the thirsd shell, three subshells are present , i.e. s,p and d subshell

So, shell is denoted by n and subshell is denoted by l