hi @imihevc welcome!
Yes, you can upgrade from the OSS version of Grafana to the Enterprise version without losing your dashboards and configuration. When you upgrade to the Enterprise version, your existing dashboards and configuration will be preserved.
What exactly is preserved? How do you know this is safe? Take a look at this other answer posted, that describes how to backup and restore a Grafana instance (this isn’t specific to OSS or Enterprise) and it’ll outline the pieces that need to be kept safe in order for you not to lose your config & dashboards.