it's your account number. It's most likely 8 digit number such as 45461780 and it should be in the first section from top where it says account information on your GIC certificate.
For rest of the info;
In order to process your refund, Scotiabank Canada will require the following to be emailed in one (1)
single PDF file to newaccount@scotiabank.com:
the 3 pages of your refusal letter as provided by the Canadian High Commission;
the original TT Receipt;
and the completed Refund Wire Transfer Form (found in the “How to request a refund”
tab of our website)
Note: the subject line of your email should state: Refund Request - IP number, passport
number and date of birth