The situation is like this.
I've got 3 killing floor servers at the moment.
First 2 i claimed while i had my old IP and the last third i claimed at a new one IP.
I need to update my old servers IPs to go on tracking but there's not a config like this in server manage.
I need your help. Tell me how to change IPs or change it yourselves because i really don't know how to do this.

You can migrate your player stats if you go to the manage page of the first one. The player history is all you can migrate to the new page.

But i want to migrate ratings if it's possible.
And after migration what to do with old servers?
Delete? Or what, because they are not working at the moment, they have another IPs

You cannot use the migration to transfer ranking. Your server will regain rank within a week if it is just as popular as rank only looks at that amount of time.

You might want to look into the DNS feature. Changing IPs can go a lot more smoothly.