What is I-485: Application to Register Permanent Residence or Adjust Status?
The form I-485 Adjustment of Status (AOS) is an application form to be filed by an alien who is physically in the United States who wants to adjust his or her non-immigrant status to immigrant status, i.e. permanent resident status, without having to return to their home country. If you were admitted to the U.S as k-1 Fiancee visa and married your U.S citizen Fiancee within 90 days of your entry then you are ELEGIBLE to apply for adjustment of status . But if you marry another U.S citizen who did not file your k-1 visa petition on your behalf then you are NOT ELEGIBLE to apply for adjustment of status.
Additional information: If you will apply for your application for employment authorization on Form I-765 and advance parole on Form I-131 together with your Form I-485 that means NO ADDITIONAL FEE is required. You may file this Form together. But if you choose to file the I-765 and/or I-131 separately after filing I-485, you must also submit a copy of your I-797C, Notice of Action, receipt as evidence of the filing of an I-485. (See reference link USCIS)