Hello, I worked in USA in 2022 as a j-1 student. And i tried to get refund my social security and medicare taxes but i didn't get refund them. Idk how can i get them?

You should first request the refund from your employer (at the time).   

If they won't provide it, ask for a statement from your employer denying your refund.

Complete Form 843  Form 843, Claim for Refund and Request for Abatement. 

Attach to Form 843:

• A copy of your Form W-2 
• A copy of the Visa page from your passport
• INS Form I-94
• INS Form I-538, Certification by Designated School Official (if applicable)
• A statement from your employer indicating the amount of the reimbursement your employer provided and the amount of the credit or refund your employer claimed or that you authorized your employer to claim. 
• If your employer would not provide a statement, provide the following information in your own statement.  Explain why you are not attaching a statement from your employer.
• Form 8316, Information Regarding Request for Refund of Social Security Tax Erroneously Withheld on Wages Received by a Nonresident Alien on an F, J, or M Type Visa (if applicable)

You will file this (above) with the IRS office where your employer's Forms 941 returns were filed. You can locate the IRS office where your employer files his Form 941 by going to Where to File Tax Returns.

Click here for information on Social Security and Medicare taxes withheld in error.

Click here for "Can I Get a Refund for Excess Social Security Taxes Paid?"