How to create boundary from joined boxes

I have a lot of stacked box and I want to make a boundary from them. Someone can help me to do this?
Thanks in advance !!!

I am quite sure this question has already been asked. Did you search on this forum or on others places on the net?

It is also good to post some file, geometry …

Thank you for your help. I’ve try to search but i couldn’t find this topic.
I will have experience for next time.
Thank you