Prometheus is an open-source time series database and alerting system.
The Prometheus data source plugin lets Grafana query, visualize, and alert
on metrics stored in Prometheus or any Prometheus-compatible backend
(for example Grafana Mimir, Cortex, Thanos).

To install this plugin, do
# ln -s /usr/pkg/share/grafana/plugins/prometheus /var/lib/grafana/plugins

Ensure the following settings are present in grafana's configuration file:
[plugins]
preinstall_disabled = true
preinstall_auto_update = false
allow_loading_unsigned_plugins = prometheus

[plugin.prometheus]
as_external = true
