Can you post a link to a scanned image of the particular chart ? .. might allow us to offer useful comment.
Graphical representations may have the Hp/OAT entry yield density height although that output is not usually identified as such.
Otherwise, for your enroute aerodrome, you know the elevation, can estimate the Hp on the basis of forecast QNH, and can use either the forecast OAT, or a sensible guess, to come up with a reasonable answer to the underlying question ....