I've been brainstorming on how reformat a set of characters in Excel. The following is a list of MAC addresses:

```
c00123837da2
c00685208b9f
c00f39fb0303
c017e60c20dc
c01de4084d1d
c020f0caf1db
c02719661782
c02b2924603d
c02f76701db5

```

I need them to be in a certain format. As an example for number one I have `c00123837da2` and I want it to be formatted as `C0:01:23:83:7D:A2`.

I would really appreciate any guidance you guys might have on how to achieve that because I have 25,000 entries to reformat.

Thank you!