This can be solved easily by drawing a Hasse Diagram..
See that all the properties of isomorphic graphs (same number of edges and vertices, connectivity preservation) are satisfied.
So option 3 is Ans
This poset has 8 nodes in hasse diagram.
So its isomorphic poset should also have 8 nodes.
So option 2 eliminated as it has only 7 nodes.
Option 1 is a chain so we cant get the cube like structure.
So optiion 1 also eliminated.
$\therefore$ Option 3 is the correct answer.
If we draw it we will get same stucture of hasse diagram as shown above.