To legally move to the U.S. based on marital status, your fiancé can apply for a visa (a K-1 visa). Once you are married, you will apply to change that status to obtain permanent residency status. Eventually, your fiancé may receive a conditional green card, or a permanent green card (after two years) and pursue citizenship if you would like. The process is highly complex and you will be required to submit to investigation and interviews/monitoring. It’s important to have a skilled immigration lawyer in your corner to protect your rights throughout the process.