2 questions that pretain to a tower defense game

The first is how would you have range for one object to detect other objects and then target the nearest object. The second question is how do you have an object point in the direction it's moving.

 

I think the first question for you should be where is the tutorial section, you won't be able to do a game if you need to ask questions like this.

To answer your questions:
To have range you can either do an overlap sphere to get whatever colliders are in range of X or you can look up a list of all targetable thinks and sift though them with variables such as range.

To get the rotation you do vector math.

If you just wanna do it there's a short 1-hour "tutorial" by 'quill18creates' and a series by 'brackeys', look it up on youtube.

 

Ay thanks man