You will have a ".thunderbird" folder in your home folder. This is where all of your emails and email accounts are. Take a copy of that and paste it into your 19.04 home folder.
Then, get hold of copy of the thunderbird appimage and open it and it should find your ".thunderbird" folder and use it in the usual way, thus populating your accounts tab inside thunderbird GUI.
You can get thunderbird appimage here:
I should say, an "appimage" is a standalone version of an application. In other words, you do not "install" it. Instead, you just download the folder and run the binary of the applicatiuon that is in the folder.