In order to become a permanent resident, an immigrant must get a Green Card. This is the essential identity document that allows immigrants to legally live and work in the United States.
According to the Citizenship and Immigration Services (USCIS) , if a person does not want to lose all the benefits that the card provides, it must be renewed when stolen, lost or about to expire.
How can I do that if I am outside the United States?
If the applicant is outside the U.S. (no longer than a year) and his or her Green Card expires in the next six months, he or she will have to request the renewal of his or her residence as soon as he or she returns to the U.S.
However, if the immigrant is outside the country, his or her Green Card expires and the renewal request has not been made, he or she will have to contact the nearest U.S. Consulate or USCIS 
office. There he or she will have to submit the I-90 form.
When must I renew my card?
If the applicant is a resident and already has the I-551 form, which is valid for 10 years, he or she must renew the Green Card six months before its expiration date.
Once requested, how can I check its status?
The request status can be checked on Internet through the following link: “Case Status Online”. If you just made the procedures, you will have to wait at least 72 hours to be able to find your data.
If the applicant has doubts, it is always advisable to call the USCIS National Customer Service Center at 1-800-375-5283. When making this call, the applicant must be ready to answer questions about the receipt number, the alien registration number, and his or her name and date of birth.