Hi there,
Welcome to the Community. I'll be happy to steer you in the right direction so you can get back to doing what you enjoy.
The CRA account number is an important number for tax purposes in QuickBooks. You would have received this number when you registered your business with the CRA. This number will be printed on T4 slips and other payroll forms. You're welcome to ask other questions in the comments below.
I'll be a message away in case you need additional assistance.