Actually mixed conditional is the easiest, you don't have to worry about rules- you can use 2nd and 3rd conditional together.
It can be past-present, past-future, present-past, present-future, etc. It simply means you can use your permutation skills and make a pair among present, past and future.
PS- You are talking about mixed conditional so I have assumed you have a good grasp over other conditionals.
You should ask your question in the Answer section of italki instead of the Discussion section.
You might want to read here https://www.ef.edu/english-resources/english-grammar/mixed-conditional/