Converting a Bulk Renaming Formula?

I have been needing to rename a ton of files, which I have been able to figure out how, but I did need to use Bulk Rename Utility first, then convert the rest with Advanced Renamer. I would love to do it all in Advanced Renamer in the future if possible.

The step I need help with is adding a leading zero to the filename if there isn't one present. For example:

1. Ballet Rehearsal-Edgar Degas.tif

would become:

01. Ballet Rehearsal-Edgar Degas.tif

but

33. Shot Marilyns-Andy Warhol.tif

should stay as:

33. Shot Marilyns-Andy Warhol.tif

In Bulk Rename Utility I was able to do this with the RegEx (1) option using v2:

Match: ^(\d)\. (?X)^(\d\d)\.\x20
Replace: 0$1_(?X)$1_

Is this possible to accomplish within Advanced Renamer?

Thanks!

Reply to #1:
Match:
^(\d) (\w+\.tif)$

Replace
0$1. $2

Make sure you are renaming file and extension.