Accessing mail in ExHD or Flash Drive

Last year I bought an external hard drive and, while trying to save old email, I moved my Thunderbird folder to the new HD. When I reloaded Thunderbird on internal HD, the old mail was gone of course, and I was unable to figure out how to read what I had saved. I've been trying to tinker with the instructions for archiving on a CD (http://home.att.net/~cherokee67/archivemailcd.html), but am not sure how to adjust these directions to fit my situation:

Click on the newly created "archive@someplace.invalid Account Name "
Select: View Settings for this Account
Click on Server Settings: Point the "Local directory" path to either your CD-RW drive, e.g., F:\Archive​

I clicked on Archive, then on Server Settings
Under Local directory I went to drive H, which is where the flash drive shows up (I simply copied the folder called "Thunderbird" from the ExHD to drive H). However, I'm not sure which subfolder to select when I browse through that folder in order to set up the new account setting for Archive.
I have tried several different subfolders and keep getting an Alert that says "Failed to connect to server someplace.invalid "

 

Thunderbird is made up, like all programs which go back to the old Netscape are of a minimum of two components which are located in different parts of the operating system, i.e. the program and its profile. In the case of TB all mail is located in the profile. In other words playing with the TB program will yield no mail. I have heard of the procedure which you describe, but have never tried it.
The best way to operate with a thumb drive is to use the portable version. The advantage of such version is that this special version of TB has program and profile in the same location. You are not saying which operating system you were using, but, typically, the profile is located in the Application Data folder, which may or may not be hidden.The folder of the common TB which is of the type abc123.default can be renamed to profile, and the newly renamed profile pasted in this type of path: C:\WINDOWS\Desktop\ThunderbirdPortable\Data\profile, where I installed my TB. I don't have my thumb drive operational, but the path will be: H:\ ThunderbirdPortable\Data\profile and you will be replacing the original profile folder. I have done this, successfully, but I created the accounts in the thumb drive installation, so the Local directory already existed.
It seems to me that you want to read mail in accounts which were not set up. However, Ramona or others may be of greater help. The procedure described by Ramona was for a CD-RW.