Not sure what you are trying to achive. But Case Comment is standard object and you can get all the Case Comments associated with a perticular case with the help of ParentId field which will be a lookup to case. A sample query might look like: Select Id From CaseComment Where ParentId = 'Your CaseId'
A sample query might look like:
Select Id From CaseComment Where ParentId = 'Your CaseId'
List < CaseComment > listCaseComments = [ SELECT Id, Parent.CaseNumber, Parent.Description FROM CaseComment];
https://www.infallibletechie.com/2016/06/how-to-get-case-details-from.html
https://salesforce.stackexchange.com/questions/37291/how-to-get-the-caseid-when-creating-a-casecomment
Thanks!