Pull value from a Fields To Grafana

Dear Community, i am kind of new here. and i am using Elastic with Graylog.
and also using Elastic as a datasource for the Grafana,
everything works fine. but now i want to pull a dynamic value from a spec field
the field contain a numeric value .
what query do i need to run in order to pull this value to my Grafana.
thank you for your help!