Does my account support Tags or Sources?

If you signed up on or before January 24th, 2017 12:00 PST, your account is using the source dimension to describe Metric streams.

If you signed up after January 24th, 2017 12:00 PST, your account supports tagged metrics.

The easiest way to see the difference is if you look at your raw metric view. The source based metrics will show rows of sources under the metric chart whereas the tagged metrics will show a table, with one column per tag.