Even though there is a TB 29 beta, there are no frequent updates for it. There is a TB 28 beta as well, but it won't get anymore updates. The current released version of Thunderbird is 24.5.0. You can get it here:

https://www.mozilla.org/en-US/thunderbird/

You likely installed what was a Beta build and continued from there. There are no Releases of Tb 25.0, 26.0, 27.0, 28.0, 29.0 as the next major version will be 31.0

On my Thunderbird page, if i click on Help, go down to the last drop down which is About Thunderbird, click on that, a pop-up titled About Mozilla Thunderbird comes up. It has a large blue bird with an envelope on the left. On the right, in big letters it says Thunderbird. Under that in small type is 28.0. Under that is a button that says check for updates. Under that it says... you are on the beta update channel. Under that is a bunch of words with hyper links to Licensing Information, End User Rights, & Privacy Policy among others. If this is not my release #, where do I find it? Thank you in advance for your help. bob

you are on the beta update channel

As said before, get the release version from the link given above.