How to add underline "_" and number at once?

Advanced Renamer forum
#1 : 19/10-20 11:14
Teodora
Posts: 1
I would like to know how can rename a bunch of JPG files with adding a number 1,2,3etc. with underline before
756_1
756_2
756_3
756_4 etc.
But, the first one should stay so:
756
756_1
756_2
756_3
756_4 etc.
Please help :)
#2 : 19/10-20 14:07
David Lee
Posts: 1125
Your question is not clear.

You are asking how to ADD an number (_x) to an existing filename but your example implies that you wish to CHANGE the existing numbers (by subtracting 1) - or alternatively that all your files initially have the same filename (756).

Please give examples of typical filenames before and after renaming.