if they are really numbers format-cell-numbers-custom
000-0-0000-0000-0
if they are text that looks like numbers
=left(A1,3)&"-"&mid(a1,4,1)&"-"&mid(A1,5,4)&"-"&mid(A1,9,4)&"-"&mid(a1,13,1)

"ian78" wrote:

I have a column 0f 3500 of numbers to convert