I would like to remove old posts from old domain and have them redirect to the new domain.

Moving the posts from one b2evo site to another isn't much of a problem.

1. Copy the database from the original site
2. Delete all the contents of the new site's database via cpanel > phpmyadmin for example
3. Import the new database on the now empty one.

Be sure you have the same version of b2evo on both sites at this point, then you can update the new site to 7.1.5 if you want.

Not sure what you mean by redirect?

I Have everything moved, that is not the issue, my problem is, if someone goes to the previous website, that post won't be there, however, it is on the new domain, that is why I wanted the URL to populate every past the hash, so it would take them to the exact post on the new site?

Apologies! If someone goes to the old URL then it will need a redirect from there. So it's a server redirect issue not a b2evo one.

Maybe this is what you are looking for

. . . use a line like this for a permanent redirect:

Redirect permanent /oldlocation http://www.newdomain.com/newlocation

There's more on the page
from https://www.digitalocean.com/community/tutorials/how-to-create-temporary-and-permanent-redirects-with-apache

If you have cpanel it may have a GUI to avoid coding.

Point your old domain to your new server and configure it as an alias domain on your server AND as an alias URL in b2evolution here: https://b2evolution.net/man/collection-base-url-settings

Once you do that, b2evolution will make automatic redirects.

See also: https://b2evolution.net/about/foreverlinks