Change xxxxxx (1) to xxxxx_1

[Admin]

I have a huge problem and I need a solution. Our webmaster has decided to change everything including the photo uploader. When I take images of products, we take a front and a back of the item so there are 2 images. In the past, I've always just selected both images, selected "RENAME" and enter the ID#. Windows automatically adds (1) to the first image and (2) to the second image.
My problem is that now I'm told I can't use (), I have to use UNDERSCORE or the program can't find it. This means that I have to rename every single image individually and there are 6,000 images.
I need a solution where I can change everything that says xxxxxx (1) to xxxxx_1 and everything that says xxxxx (2) to xxxxx_2.
Can your program do that?
Thanks,
Joe

[Admin]

Use RgeEx (1)

Match : %1 (%2)
Replace: %1_%2

Enable option Simple in RegEx (1)