Reviewing the screenshot you provided, you still have the old AssetStore version of the TextMesh Pro package in your project.
Since the TMP package is included in Unity by default since 2018.x, you get those errors because you have two distinct versions of TMP in your project.
A few additional questions before providing a solution.
Since the legacy AssetStore versions of the TMP package use a different set of GUID and FileID, you have to migrate from the legacy versions to the Package Manager versions.
Do you recall doing this migration? The process is outlined in the following sticky thread . Most users did this migration when moving from Unity 2017 to 2018.x.