You would need to use another column with a formula.
It all depends on what you need the 8 digits for.
A1 = 12345678901234
=RIGHT(A1,8)
That will return the result as a *TEXT* value.
=--RIGHT(A1,8)
That will return the result as a *numeric number*. However, Excel doesn't
like numbers that have leading zeros so it drops any leading zeros.
A1 = 12345600001234
=--RIGHT(A1,8) returns the numeric number 1234
What you can do is format the cell as Custom using this format: 00000000
Then the result will be 00001234
However(!!!), the leading zeros are for display purposes only. Excel still
doesn't recognize those leading zeros. This can be important if you need to
perform further calculations on the "numbers".