Minecraft is a sandbox independent video game. A nether portal is one which behaves as a gateway between the overworld and the nether. Minecraft calculator is used to find the relative coordinates between the Nether and overworld. Thus you can find the coordinate to built the return gate.
If the Nether co-ordinates are 2,3 and 5, the overworld co-ordinates would be,
X = 2x8 = 16
Y = 3x1 = 3
Z = 5x8 = 40
Using this minecraft portal calculator to find X, Y, Z coordinates from Nether to Overworld or vice versa will provide you with the best possibility to be hooked back at the right gates.