I suggest you do a backup first. The downloaded file will overwrite 102.

Best practice. 1st Uninstaller tb102 and then install tb115. Profile will be recognized without any problems.

Good information so far. I have downloaded a compressed file of 115. What do I do, step by step please, to get this installed?

Download from https://www.thunderbird.net/en-US/thunderbird/all/

As I said, I have downloaded the file. What do I do with it?

JC

Just do as instructed

The simple approach is to exit Thunderbird and doubleclick the downloaded file and follow the instructions. Either that, or use Windows to uninstall thunderbird and reinstall. All I did was the simple approach.