How do I do I unwrap from a point of view? How do I unwrap this object from my point of view, so that is perfectly aligned with the mesh behind it?

As you can tell in the following image, I tried my best to position it myself, but took a long time to get it how it looks. Any tricks or tips?

Thanks for your time.






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Edit: I was told I missed some details so here some more
https://i.gyazo.com/45f9298ce16cfe784d6f30ebdf7e1df2.png
You See this tiny cube that out of line with the mesh behind it we will call the mesh behind it mesh1 and the tiny cube that out of line mesh2
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So I want mesh2 uvmap to be aline with mesh1 uv map perfectly without affecting mesh1 uvmap I hope this make since 
thank you for your time once again
You can try this:


Select your objects and go to edit mode
Select all faces of the both objects and switch to Top view
From the menu select UV -> Project From View
Switch to object mode and create a material for one of the objects
Add your texture to the material
Make sure you create a Texture Coordinate node and connect the UV slot to the Vector slot of your image texture.
Apply the same material to the other object.




Edit:

This was added to the question:
"I don't want to affect the plane UV map"  

In this case you can use the Data Transfer modifier on your Cube to transfer the UVs form the Plane to the Cube (I used a Torus instead, it's a bit more visible)  


Position the Cube somewhere above the Plane
Use Data Transfer modifier on the Cube
In the modifier settings as the Source select your Plane
Check Face Corner Data with Nearest Face Interpolated settings
Click on UVs
You might need to click Generate Data Layers  


For the Data Transfer modifier to work properly you will need more edges/subdivision on your Plane.
If you don't apply the modifier you can move your Cube and the UV data will adapt to the new position.