Some general information is at https://docs.civicrm.org/user/en/latest/case-management/what-you-need-to-know/#system-status-warnings but in an established install like yours you might need to poke around a bit and it will be specific to that install.
First, make a backup and do any fixing on a copy first just in case.
Then for your install it sounds like ...
Thanks to @petednz-fuzion, solution was very simple:
install the Related permissions extension which is already included in CiviCRM extensions and that you can add from : domain.com/civicrm/admin/extensions?reset=1
Set the parameters the way you need at: domain.com/civicrm/admin/reltype?reset=1
Select the relationship type you need to set
Scroll down to ...
Welcome to StackExchange Helen!
I am not aware of any core function that can do what you want. With a little bit of coding or manual work (import/export) you could try an approach like this:
Create custom fields for the individuals that can hold organisation
Create a skript or use an extension like SQL-Tasks or CiviRules that copies all ...