I have a Android app that was working on my other computer, but when I'm trying to run it using my other computer (with Android Studio Arctic Fox | 2020.1.1) I get the following error:

"com.android.tools.r8.internal.r8: Dex file with version '39' cannot be used with min sdk level '26'."

Execution failed for task ':app:mergeProjectDexDebug'.

• A failure occurred while executing com.android.build.gradle.internal.tasks.DexMergingTaskDelegate
  • There was a failure while executing work items
    • A failure occurred while executing com.android.build.gradle.internal.tasks.DexMergingWorkAction
      • com.android.builder.dexing.DexArchiveMergerException: Error while merging dex archives:

What is the easiest way to fix this?
And how can I avoid getting errors like this in the future, when moving a project from one computer to another?