The UCI # will be on the bottom left corner of the visa stamp. This is probably the case with Visa stamps issued after 2010 or so. Check the below link for example:Thanks for the reply. And about the UCI and application number on top of the form , what should we write?
https://www.canadavisa.com/canada-immigration-discussion-board/threads/parents-and-grandparents-sponsorship-2018.513951/page-109#post-6838178