Hi and welcome to the forum 
First off: Foreman is currently not supported on RHEL9 (due to various version dependencies), so you will have to settle with RHEL8 for now. There is a lot on that topic in Path to Ruby 3.0, 3.1, EL9 and Ubuntu 22.04 in case you are interested.
Otherwise: Afaik there are no tools to assist in such a migration. Depending on what you are comfortable with, you might find success with hammer, the API, ansible with the foreman-ansible-modules or maybe even copying things from hand. On the plus side, the changes from Puppet 5 to Puppet 7 have not been that major, so I would expect most things to just work out of the box.