Well. CBC and 3DES are separate things. Although I never heard of 3DES used in any other mode than CBC.
Anyway, if you want to enable 3DES you may try cipherSuite setting in [SSL] stanza of server.conf or in appropriate inputs.conf stanza. But you really shouldn't do that. 3DES is not considered secure and TLS1.3 explicitly doesn't include this suite.
Thanks for your answer,
1. Do these changes are to be made in indexers or Universal forwarder??
2. Do i want to configure/change anything in the certificates?
Depends on the rest of your configuration. TLS negotiation is - as the name suggests - a negotiation so both sides participate in it to find overlapping set of parameters acceptable to both sides. So if you set one side to accept only 3DES-CBC and the other to stick to AES-GCM the negotiation will fail.