upgrade from version 2020.1.17 to version 2020.2.0,got message as following when upgrade from version 2020.1.17 to version 20202.0

Questions & Answers
1

Assembly ‘Library/ScriptAssemblies/Assembly-CSharp.dll’ will not be loaded due to errors:
Reference has errors ‘UniFileBrowser’.

Assembly ‘Library/ScriptAssemblies/Assembly-CSharp-Editor.dll’ will not be loaded due to errors:
Reference has errors ‘Assembly-CSharp’.

Assembly ‘Assets/Plugins/UniFileBrowser/UniFileBrowser.dll’ will not be loaded due to errors:
Unable to resolve reference ‘Boo.Lang’. Is the assembly missing or incompatible with the current platform?
Reference validation can be disabled in the Plugin Inspector.
Unable to resolve reference ‘UnityScript.Lang’. Is the assembly missing or incompatible with the current platform?
Reference validation can be disabled in the Plugin Inspector.

2

when you upgrade a unity project you have click the project then there will be this messange this project was created from a older/newer version of unity please upgrade/downgrade your project so click upgrade then will open and verify unity it will be unity version(example) was downloaded from the internet then click open and it will upgrade/downgrade @LemonKetchup