Number files in same way

Hello, first of all, thank you for such a great, free tool. It's been amazing and easy to use so far.

I have a bunch of files with the same name but different extensions. I want to rename them all together. How can I have files with the same name keep the same number?

For example, currently, I have:
006_fileA.jpg
006_fileA.txt
009_fileB.jpg
009_fileB.txt
006_fileC.jpg
006_fileC.txt

I want to rename to:
001_fileA.jpg
001_fileA.txt
002_fileB.jpg
002_fileB.txt
003_fileC.jpg
003_fileC.txt

Thank you very much again for this great piece of software.

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