Yes, just
manually import the hands from the HM3Archive folder* and HM2 will import the hands you played on HM3. Note: HM2 may not support all of the hands/sites you played with HM3 depending on the sites/games you play.
*All original hands that are auto-imported get moved to an archive for performance reasons. Your \HM3Archive is in C:\HM3Archive by default, but you may have put it anywhere. The archive should be organized by \Network\Month\DayOfMonth (example: C:\HM3Archive\SiteName\2016\07\31).* It is configured in the Tools - Settings - Import menu.