You need to submit a properly completed and signed Supplement J. Confirmation of Bona Fide Job offer or Request for Job Portability Under INA Section 204(j), showing that the offer of intended permanent employment as stated in the form I-140 immigrant petition continues to exist.
Please refer to the below USCIS links for the details.
Disclaimer: This is not a legal advice. Please consult with your immigration attorney for the legal help.