Welcome to the forum.
Just open the project using X5 and RoboHelp will do all that
for you. It will create an XPJ file which is what you will normally
use to open the project in future.
There's a chance you will encounter a problem printing and
that is covered in Snippets on my site.
Help others by clicking Correct Answer if the question is answered. Found the answer elsewhere? Share it here. "Upvote" is for useful posts.