Cells containing something like 1234-56 or 1234-56.78.9 are going to be text strings, and number formatting is not going to do much with text strings. We will probably need a better understanding of exactly what you want to do here. Are you entering numbers but want them to appear as text strings? Are you entering text strings, but you want to display the text different from the entered text value?

If I enter 9 digit numbers (123456789) and then use a number format code like 0000"-"00"."00"."0, then I can get 123456789 to display as 1234-56.78.9, but be very clear in your mind that the underlying cell value of such a formatted number is still 123456789. Something like 1234 will display as 0000-01.23.4. Something like 123400000 will display as 1234-00.00.0.

Help us understand better what you are wanting to do here (what value are you wanting to enter into the cell and how do you want that value displayed). I'm not certain that number formatting alone will achieve what you want, but we can explore possibilities when we better understand your goals.