How can I check that my marketing cloud Org is available for connecting with the Salesforce CRM ,ie, in the documentation it is mentioned that "Marketing Cloud account must be provisioned and enabled for use with Marketing cloud Connect prior to connection ", where can I validate this in Marketing cloud.
You go to the Admin tab of Email Studio (you need to be administrator role to see this). If you see "Salesforce Integration" in the menu on the left side it is enabled.
If you have multiple business units it's best to check it in the account level business unit. In one customer account we had the effect that it didn't show the admin option at sub business units. It turned out to be an issue with the system itself but it if you are affected you might jump to the wrong conclusion.