That's interesting Tony. A 300mm EQ 2.8 macro would be awesome. I didn't know Sigma ever made that lens for M4/3. Judging by the link you referenced it sure appears to have a M4/3 mount but of course I can't be sure. The Sigma 105, 150, and 180 were all excellent as you probably know
I'm thinking you would probably need the same adapter you would use for the Olympus 50-200 2.8/3.5 ??
This link was from 2014