Hello aspirant,
As per your date of birth you will be 21 by the year 2024. The Eligibility criteria to appear for upsc is that the candidate must be 21 years of age and should be less than 32 years as of 1 August 2024 . So YES you can appear for Civil services Examination. Another criteria for Eligibility is that you must have a graduate degree from a recognised University.
To know more about the exam visit the following link
https://competition.careers360.com/exams/upsc-cse#:~:text=Candidate%20must%20have%20a%20bachelor's,the%20UPSC%20IAS%202022%20examination.
All the best !