You can see the Missions at the bottom right corner of the screen along with other menus. It's the first menu you can see titled "Mission". It consists of three parts: The Daily Rewards, Missions(Growth and Side Missions) and Research Tasks.
Daily Rewards[]
Each target you hit opens a crate, so finish daily tasks before the countdown timer refreshes for fantastic rewards and alliance EXP. Every day, you can claim up to 7 boxes! Claim by tapping on the crates!
To see full details about Daily Rewards go here.
Missions[]
Growth Missions
Growth Missions are tasks you'll complete along the way.
When you're done with all your mission, you will find this message as seen in the picture below:
Side Missions
Side Missions are extra missions you can gain as you progress in-game with good rewards. Some include upgrading buildings, upgrading heroes, killing infected, finishing research, and training troops.
When you're done with all your mission, you will find this message as seen in the picture below:
To see full details about Growth and Side Missions go here.
Research Tasks[]
Completing Research Tasks will speed up the timers of the target Research. The Research will only be sped up after the completed Research Task is activated. The target Research timer will be reduced no matter if has been started or not. Research Tasks are refreshed every two (2) days.
To see full details about Research Tasks go here.