I did have the Get Text activity into ClientDetails already coded.
I just applied your formula (copied below for reference) into the 3 fields ClientId, ClientName and ClientCountry respectively:
ClientDetails.Substring(ClientDetails.IndexOf("Client ID: ")+"Client ID: ".Length).Split(Environment.NewLine.TocharArray)(0)
After concatenating the 3 fields into the HashResult field and typing into the Hash Generator it looked as follows which was perfect.
This solved my issues. will mark it so. Thank you very much !!!
PS:It is clear that string manipulation is complex and unfortunately it is not covered in detail in any course offered. It would be good for the academy to offer a course on string manipulation. where can one get a user guide for syntax and commands?.