does pi-hole is good for largescale enterprise as a DNS server?

Hi Team
i would like to know whether pi-hole is good and scalable for largescale enterprise (approx 10000
clients)

If yes,let me know what is the recommended ubuntu server configuration for handling 10000 clients.

and also like to know what is the backend server used for pi-hole

See here:
https://docs.pi-hole.net/guides/benchmark/

For general purpose DNS? There's other DNS servers that are better suited to the job.

Your network administrator will be able to tell you that information. Number of clients is not representative of server load.