I have a compiler error that I have no idea how to fix

Unity Engine
1

Today I imported a project from and older computer onto a new one but when I tried to do a test run it gave me this error message:
C:/Users/[my name]/OneDrive/Desktop/projects/Galaxy Shooter/Library/PackageCache/com.unity.textmeshpro@2.0.1/Scripts/Runtime/FastAction.cs(24,45): error CS1644: Feature `out variable declaration’ cannot be used because it is not part of the C# 4.0 language specification

I think this may have to do with the fact that the older computer had been running an older build of Unity. I don’t know for sure which one, but it’s probably one from early to mid 2017.

I know how to access the file in question but I have no idea what to do with it. Do I delete it or reconfigure it or something?

2

Probably related to this:

There is a project setting that you may have to change in order for TMP to work now.