For this achievement you need to completely explore an area 1,500 times. that's a lot.
While playing missions you will notice there are notifications popping up saying 25%, 50%, and 75% explored. after that you will get a badge for exploration, this means you have completely explored the area. do this 1,500 times and the achievement should be yours.
Track your progress on this sitehttps://www.stormshield.one/