i am in HMA ... how do i get LMa units without moving up in age?
You can't always get the next age(s) of units. Especially early ages tend to have age-locking blocks to stop you. While the following list is not warranted to be 100% accurate as sometimes other lines of the story may allow you to get ahead further (peace vs war, or fighting one side or another or both on some maps).
You can get X age troops by Y age:
EMA by IA (barbarian bonus area)
Colonial by LMA (LMA bonus area)
Progressive by Colonial (Story)
PME by Progressive (Story, possibly earlier as there's also a sidequest in PME to get commandos that was unlocked by a map action while i was in PME - i'm not sure if it's only a map requirement or if you have to be past a certain place in tech/story as well)
CE by PME
AF by CE (possibly even OF - depending how many techs you have saved you may need to advance to TE as there is a lock at the end of the CE story that requires to research a tech near the end of the age - so tech researches later in the story have to come from skipped techs earlier in the tree).