Hello Pradhan
You can create your payment term in ECC and it should be updated to table CRMC_PMNTTRMS in CRM system.
Terms of Payment are part of the customizing object DNL_CUST_PRICE. You can use a request
load to bring across the new terms to CRM. This can be done by first creating the request load in R3AR4. Then you can run the request for the specific terms of payment from transaction R3AR2.
You can also take a look at the following note
1420329 - FAQ: BTX: Payment terms in CRM.
Bernadette