The application MGCPAPP command is no longer supported in latest Cisco IOS versions.
This is the new command:
dial-peer voice 8000 pots service MGCPAPP port x/x/x
Issuing the service MGCPAPP command enables Media Gateway Control Protocol (MGCP) on the dial peer.
Note: Do not use this command in dial peers that support PRI backhaul or BRI backhaul.
For Related information, refer the following documents