I have no idea why you are looking in applications. Thunderbird profiles in macs are in ./library, which I understand is hidden. (Never used a mac since they had colour screens.)

Go to the help menu, open troubleshooting information and click on the show profile button in there to locate the profile in use on the mac. Then past the relevant files from the windows profile into that with Thunderbird closed. (if you are not asked about replacing files you are probably copying in the wrong place.

Hello Matt, I apologize for the delay in replying and thank you for your response. I was following the guidance on the Mozilla website (https://support.mozilla.org/en-US/kb/installing-thunderbird-on-mac). Which help menu are you referring to? I will follow your instructions and will let you know the results. Again thank you, take care and be safe.

Is there anyone who can help me with this issue? Thank you.

I did a web search for thunderbird profile mac and found a page on locating the profile. I found this text: ......

   Start Mac and open the Finder window
   Now, you can click on Go Menu and then navigate to Go to Folder. Else, you can directly use Command+Shift+G in order to open Go to option
   Here, type or paste ~/Library/Thunderbird/Profiles/(Profile name)/. After that enter the profile name you want to open in place of profile name. In case you are unaware of the profile name, remove the profile name part from the path

...... I don't know how to copy the profile folder but it appears to belong at ~/Library/Thunderbird/Profiles/ If you can get the profile folder there, then start TB, click to help>more troubleshooting information. Then scroll down to profiles and click about:profiles in the right. That brings up a panel where you can browse the existing profiles. If you don't see yours, click 'create profile, type in a desired name (first) and then click the browse button to locate your desired profile. Then you can click to make it the default. I hope this gets you to a place where minor issues can be resolved. Keep me posted.