Easy Question - filter schema.measurements

I have this to get a list of my measurements but I want to populate a dropdown in Grafana with just a few. How do I filter the results?

bucket: “mybucket”

Somehow I want this added in there: |> filter(fn: (r) => r["_measurement"] == “RTPLPROHISTORY.FIT_0300.SCALED”

but I’m not sure how to filter the results of the output… thanks for any help. I googled and googled…