When tried to access templates in Tridion content manager it shows error
“Unable to get template types with id:#number”.
Also the templates in content manager is not accessible
Looks like you have a Template Type defined in your Tridion.ContentManager.config file which cannot be loaded. Perhaps you uninstalled something and the configuration file hasn't been updated -- or you restored an old configuration which refers to a Template Type that isn't installed anymore.
Either way, looking up the exact ID in the configuration will tell you which type it is -- you can probably figure it out from there. If it's something that isn't in a default Tridion installation and you don't need them, feel free to remove the line or comment it out. That should get rid of the error.