How to view the contents of the following files together:

I think the simplest way is to use more or less of the pager.
(Assume that only files that can be displayed as text exist in this directory)

$more*.txt
   or
$ less*.txt

more automatically moves to the next file when it terminates.
For less, navigate to the following file in :n.

 find.-type f | xargstail-n+1

or

find.-type f-exec cat{}\;

would be good.

cat-How to display contents of all files under a directory on the screen using unix commands-Stack Overflow

command line-Show contents of many files-Unix&Linux Stack Exchange

I think pr is better if you want to display it with a file name and line number.

 find.-type f | xargs pr-n-f | less

find.-name "*.c" | xargs pr-n-f |less

With zsh, ** you can write wildcards that match multiple levels of directories, so for example,

$wc**/*.h

Then you can wc only the "*.h" file, including the ones that are deep below the current one.

[Edit after posting]
If you simply want to view the contents of the file, you can use commands such as more and less as well as cat.