Do you need to consolidate the meaning of Third Conditionals? Here's a worksheet which practices the meaning and form of Third conditional if-clauses. It asks students to make up sentences according to the given situation. It's an ideal worksheet which only focuses on type 3 if clauses and can accompany a lesson after the grammar presentation stage.
Be careful at the seventh exercise of the worksheet. It uses "prepared" as an adjective which may confuse students with the past simple verb form. Consequently, they should use "had been prepared" in the answer which is also confused as a passive form.
encourage peer review in the feedback stage
I strongly suggest you encourage peer review in the feedback stage. When students check each other's answers, there'll possibly be more room for discussion and students will get more of this worksheet.
A QR code suggested answer key for your homework assignments is added for your convenience.