Looking on the internet deeply has found these results:

you should have prepared is the most popular phrase on the web.

you should prepared 126,200 results on the web	you should have prepared 1325,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Because we have prepared a scene from that film For your viewing pleasure. The authorities in Morocco have prepared a vaccination strategy. I have prepared severance package that is more than equitable. The ladies have prepared a show. We have prepared our proposal with the aim of maximising the efficiency of Community spending. That is why I have prepared a surprise... The technicians have prepared the file I'll be sending. You have had the time, and you should have been prepared to answer.

you should prepared

126,200 results on the web

you should have prepared

1325,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Because we have prepared a scene from that film For your viewing pleasure.
The authorities in Morocco have prepared a vaccination strategy.
I have prepared severance package that is more than equitable.
The ladies have prepared a show.
We have prepared our proposal with the aim of maximising the efficiency of Community spending.
That is why I have prepared a surprise...
The technicians have prepared the file I'll be sending.
You have had the time, and you should have been prepared to answer.