Find and Replace Question

[Brad_Bensons]

Hi all,

I need to change the name of over 2000 images. The images end in -1 and -2 etc but I need to replace them with _1 and _2 etc. 

The trouble I have is that some of the file names also have a - throughout so replacing all of the - with _ doesn't work. I've found a common theme is that they all have a _ as either their second or third last character. Could somebody let me know how I may be able to adjust these all without doing it manually?

[Stephen_A_Marsh]

In the Batch Rename dialog, one possible option using String Substitution + Regular Expression would be:

Find:

(.+)(-)(\d+)(\.[^\.]+$)

Replace:

$1_$3$4

[Brad_Bensons]

This is almost perfect. Thank you.

Is there a way to restrict it to changing the _ only if there are 2 characters after it? 

An example of a file I don't want changed: BA-48807 (this is the full name of the file and needs to remain the same).

[Stephen_A_Marsh]

Certainly:

(.+)(-)(\d{2})(\.[^\.]+$)

P.S.: BA-48807 should not have been affected, at least it wasn't in my tests...

[Brad_Bensons]

Beautiful, I apologise for not being clear, I meant up to 2 characters haha. 

So for example. File names that should be changed (> what they should be changed to):

ABCD-1 > ABCD_1

ABCD-12 > ABCD_2

File names that should not be changed:

ABCD-123

[Stephen_A_Marsh · Accepted solution]

If not exactly two, but possibly one or two digits...

(.+)(-)(\d{1,2})(\.[^\.]+$)

[Brad_Bensons]

Wonderful! This is perfect. Thank you so much!