You did not explain how you copied. If you used thunderbird's zip export, it REMOVES passwords. A better approach might be this:

Here is the link for moving a profile in Windows when installed in default location:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
8. start thunderbird and all should be there

Unfortunately, there is no simple answer. If the old computer is accessible you can start thunderbird, click settings>privacy&security and retrieve passwords there. Those may work unless you are using an account requiring Oauth2.

Hello David, Many thanks for your help. Sadly all my efforts to establish Thunderbird on my new laptop have failed. Mozilla seem to me to be obsessed with passwords none of which are known by me. I followed your instructions but the actions you suggest are beyond my 87 year old brain So I have decided to abandon my effors and seek an alternative program for my emails in future. I am grateful for your efforts and wish you well. Alan Laitt

Alan, If you do not recall your password, other email solutions will also fail. One possibility is to create a free account at gmail.com or at gmx.com and then access it from the browser. That approach can work well. Good luck.

You could access your email via the service's web interface and try the 'Forgot password' link.

Thank you very much Ed. I am still not able to access Thunderbird. I have concluded that this is beyond my ability and I have decided to abandon my efforts. I do have email access using Plusnet Webmail. It is not as effecient as Thunderbird was but it does still enable me to receive and send emails. Many thanks for your efforts and patience, Regards, Alan Laitt.