I'm married for 12yrs legally . Separated for 11yrs now and I don't know where my husband is

Where you live may make a difference, In the US, yes. You will of course have to make attempts to contact him, and/or locate him. Then if not found, do service by publication.

If you want a divorce you have to file for one. Not being able to find your husband just makes it a little harder to process.