Where a database of different z values of redshift can be found?
There are some great databases with a lot of information in them, when you found the galaxy you looked for, somewhere on the page there should be redshift information if it is has been measured at some point.

The NED/ipac database is quite nice for galaxies (https://ned.ipac.caltech.edu/).
Or SIMBAD is also great (http://simbad.u-strasbg.fr/simbad/).