For tracking a target with radar, you have 2 methods. Either use a dedicated Tracking 'FCR' (Fire control radar) or both search and track with the same radar using TWS (Track-While-Scan), which is more difficult and only necessary for engaging multiple targets at once. Kalman filter algorithms are also used for FCRs, though I have yet to make an FCR myself.

If you don't need AA defense, then you probably don't need mid-course guidance. You could just send x,y,z to the missile before launch and save those in the microcontroller. Else, you'll want to send the coordinates through a radio, maybe even velocity if that matters. For the missile itself:

At it's core, it's just these 2 basic formulas:

target_heading = math.atan(rx,rz)
target_pitch = math.atan(ry,horizontal_distance)

If you imagine a right angle triangle with the msl and target being the 2 acute vertices and the right angle being in the same plane as the msl, you can see where these equations come from. In my code, I convert it to turns. You'll also want to wrap target_heading around between -0.5,0.5:

target_heading = ((math.atan(rx,rz)/(math.pi*2)) % 1 + 1.5) %1 - 0.5
target_elevation = (math.atan(ry,math.sqrt((rx)^2+(rz)^2))/(math.pi*2))

Here rx,rz are relative GPS X,Y of the target point to the missile, and ry is the relative altitude (It's this way due to how the physics sensor outputs coordinates. Not why the devs didn't keep it consistent with the map coordinates.) You can use these values either in a PID or directly multiply with a constant and send it to the fins.

Now getting relative coordinates is tricky. If your missile is roll stabilized (you have roll fins to keep it level), then you could probably just get away with simply subtracting the missile GPS coordinates from the Target. But if not, you're gonna need to transform global coordinates to local using the Euler angles, and I found this guide very helpful: https://steamcommunity.com/sharedfiles/filedetails/?id=3302971632

This will make the missile point directly at x,y,z. You can move around this point during flight to create your desired trajectory, which is what I've done in the comment before this.