Regex to extract account number from a path with specific format

[Gokul_Jayakumar (Gokul Jai)]

Hello @mnlatam , Try this regex expression
(?=123)\d{12}

System.Text.RegularExpression.Regex.Match(YourString,"(?=123)\d{12}").ToString.Trim

regex101: build, test, and debug regex

Regards,
Gokul Jai