April 2023 is the final patch for SharePoint 2013. It is the patch you should have in all of your farms.
To see which build your farm is, go to Central Administration > System Settings > Manage servers in your farm (/_admin/FarmServers.aspx)
Or using Windows PowerShell: (get-spfarm).buildversion
To see which build your farm is at with Fiddler, open the site in question and view Inspectors > Headers and under Miscellaneous check the build under MicrosoftSharePointTeamServices header.
To see which build your products are, go to Central Administration > Upgrade and Migration > Check Product and patch installation status. (/_admin/PatchStatus.aspx)
To greatly reduce the time it takes to patch a SharePoint 2013 server, read this blog post by Russ Maxwell, Why SharePoint 2013 Cumulative Update takes 5 hours to install? It explains why the process takes so long and provides a handy script that makes the patch install much more quickly. Do yourself a favor and check it out.