Salary slip

After successful completion of my internship the job was mandatory that was not the issue but the person extended my internship date by 10 days so i had a talk he told that u have not submitted kra etc so when you will submit that well talk then so after submitting the kra he handed the offer letter and date was still the date extended by 10 days so now i just signed that offer letter n later i realised the date so he told we will look a month for your performance if its good then those 10 days will be excluded from internship n so but that later did not arrive and then march came lockdown happened so now i have to join the new company i dont have any doc not the salary slip because he does not provide any its just mentioned in the hr policy but have not received any salary slip.being my first job i was not aware about salary slip etc no offer letter because its lost now i had kept that in my office drawer and also no appointment letter. And the notice period is also 60 long days. So i want advice regarding not having offer letter and appointment letter and salary slip law.