I’m assuming the r500 is an unleashed version. If you have access to it and you are able to login to it. You can go to the admin and services tab and go to the backup and restore option. From there you can do a factory restore option. Assuming you have only 1 r500 or 2.
Once you do the factory restore ...give it about 5mins for it to do it’s thing.
Anyway, before you do this you should have your isp router plugged into the switch at the home.
After doing this reset just follow the instructions this video, it might look a little different since your r500 might have newer unleashed firmware. https://youtu.be/j8I5aVwMNMg