Sixty (yes 60) minutes of CONTINUOUS exercise practice on a ROWER. You could use an ELLIPTICAL or RUN or a BIKE/AirDyne or whatever you want.
I would expect an average HR of <90% (less than 90%), please see yesterday's post on how to roughly find your Max HR if you do not know.
I suggest around 80 to 85% maxHR in order to get a good beating. If you have never done 60 continuous minutes of any training practice then maybe you want to scale it. Or do it slower.
I believe the value of the 60 minute workout is to shut the voices in your head that urge you to QUIT.
The more intensive it is (higher HR) the louder the voices in your head and the higher the effect of the exercise prescription.