As per the CRA: If you were not a resident of Quebec on December 31, 2023, and you contributed more to the Canada Pension Plan (CPP) than you had to (see line 30800), claim the overpayment on line 44800 of your return. The CRA will refund the excess contributions to you or use them to reduce your balance owing.
When in your return under refund or amount owing top left - you will see a drop-down arrow- click on it and click on View detailed tax summary, you should see your overpayment CCP amount on line 44800.