Hi there,
Thank you for getting in touch with us, we do appreciate your time.
The best and fastest way to do this would be to export (Maps -> Advanced/Tools -> Export) your markers, use a code editor or “Replace All” related feature to replace your old domain with the new domain that you will be changing to, then import (Maps -> Advanced/Tools -> Import) your markers to your map again.
Should you need assistance with this, I am more than happy to assist.
I hope this helps?
Kindest Regards,
Matthew