Here's a helpful sentence making worksheet on the mixed type of conditional clauses. Your students just need to read the situation to make up appropriate sentences using mixed conditional, which summarises the situation in short.
encourage pairs to check each other's worksheet
The answers to each question can be expressed in different ways, so be ready for different approaches and explanations to each question. I think letting students check the answers in pairs is a brilliant way of utilising this material in your EFL class. It'll start fruitful discussions for consolidating Third Conditionals.