Are Risk 2210 A.D 3.0 MODs considered as 1 unit or 3 units?
Risk 2210 uses the same base rules as classic Risk.

From the rulebook, page 2:


  If you have a question not answered in the  RISK 2210 A.D.™ section,
  then refer to the Classic RISK® rules


In classic risk, "units" and "armies" are synonymous.  The higher denomination pieces are just for player convenience.  Thus, with a 1.0-MOD and a 3.0-MOD, you would roll 3 dice on the attack, just the same as if you had four 1.0-MOD's.