Unless you are running Unity 2017 or older, you should be using the Package Manager versions of TextMesh Pro. The AssetStore releases are considered legacy releases and no longer being updated.
Please see the following Sticky Post about migrating from a Legacy version of TMP to the latest package manager releases.
If this is a new project, then simply remove the old version of TMP from the AssetStore by deleting the “TextMesh Pro” folder and then in Unity 2018.4 or newer, use the Package Manager to update to the latest release of TMP.