My step daughters mother left the country almost 3 years ago and had only contact her 4 times in this times, what are options to have her mothers parental rights removed so I can adopt her ?

It can vary by where you live. Normally your husband will have to file for the adoption, an attempt to notify the mother will still have to be made to have her either sign over rights or attend the court hearing ( if she wants to) In many US states there is no real adandoment laws as it relates to custody, merely to child support payments.

First is there a child custody order in place, who has that custody, assuming it is your husband, is the ex paying support

The fact that this is international (as the birthmother left the country) would mean that you should consult a lawyer.

This is going to get way to complicated in the courts to NOT have a lawyer.

This is not abandonment law, this is adoption law. What you want is to adopt! To be able to do that the bio mother needs to assent or have her rights terminated. You may be able to use abandonment as grounds to involuntarily get a TPR.

I agree, you will need an attorney. Getting a TPR to clear the way for an adoption is all part of the adoption process. You don't do it separately. So get an attorney to prepare the adoption petition and get their advice on how to deal with the mother.