If you downloaded this product using Unity 4, you received the Unity 4 version of this.
If you downloaded this product using Unity 5, then you received the pre-converted Unity 5 version of this.
You do not need to install the Unity 4 version, and then convert it to Unity 5. We have already done this for you. Simply download using Unity 5.
However, if you decide to use the Unity 4 version and convert to Unity 5 later, keep in mind that all baked NavMeshes will be automatically removed, resulting in tons of errors. You will simply have to rebake all NavMeshes in every scene. Additionally, older PlayMaker versions will throw a few errors so be sure to update PlayMaker as well, taking caution during the upgrade process, since some users reported that Unity unlinks the PlayMaker FSMs after upgrading, forcing you to manually add all PlayMaker FSMs to prefabs.