Earth as a global society has made standard conversations from one unit to another with a defined set in metal the single units for some of the values. If we did find another species we should use the speed of light in a vacuum or maybe other values such as pi or e to understand the unit conversations from our language to theirs. Have you seen the movie Arrival? Spoiler but if i remember right they speak to the Earth lady using math.
Our gravity being 9.8m/s isn't a fixed value but it's based off of the integral of G (a constant) the mass of one body, the mass of the other body and the distance from one body to the other body. Which essentially is the force of each particle from one body against each particle in the other body. As far as we know, which yes might be limited, this calculation works for all bodies outside of an event horizon.
Edit:
Forgot about the wink... That might work or it might get you arrested good luck either way ?