I published a form in my home computer. However, I scanned the collected forms in my office. If I want to process them in my office computer, there is no publication ID associated with the home-published form in my office computer. Is there a way to carry/export the publication ID from my home computer to my office computer?

You have to load the database from your original computer to the other one. The location of the database and system.password file can be found at this site: http://www.formreturn.com/support/backup - just copy the files across and move the old ones somewhere else. Be sure to shut down both programs on both computers first before you do it.