Yes, you need to obtain official transcripts from all post-secondary institutions you have attended. There is only 1 exception to this rule, and that is when your current institution’s transcript lists all of the following: the previous institution name, the course title, date (e.g. semester/year), and number of credits received for all individual courses. All credits taken at previous institutions must be included.
If even one of these is missing from the transcript, you must obtain an official transcript from the transfer institution.