Garmin Website - User Manuals - Sept 2019 revision - page 7 - upper left corner.I can't find any reference to a 'Grade' field in any of the Etrex 10, 20, 20x, 30 or 30x manuals I have looked at dated 2011-2015, they do refer to Ascent (and Decent), Average, Maximum and Total rates, which may give you the data in a different format
But I would guess that the only feature you may need is a unit with an electronic altimeter that measures barometric pressure rather calculating altitude from satellite data, the error in the latter might make 'Grade' unusable because it would be too unstable.Some data fields require you to be navigating or require ANT+ accessories to display data.
The problem could be that the units you are using are not new enough to be compatible with the new software that has the 'Grade' feature said:Sorry for the delayed response, been layed up in the hospital for about a week and a half.
Both units are new with in the last 3 months.
Etrex 30x w/software version 3.0
Etrex 10 w/software version 3.70