I am wondering if there is a way to add a symbol in the same place in multiple rows using a formula.

EX: 0010055C
0010260C
0010860C

I need to add a "-" (dash) after the first three digits, so it looks like this:
001-0055C
001-0260C
001-0860C

There are 1354 rows I need to do this in, so if there is a formula it would help out a lot!
Thank you.